ST16C554 / ST16C554D / ST68C554 Datasheet by MaxLinear, Inc.

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/\ MAXLINEAR V _________________‘ INT RXRDY“ A- INTSEL
• www.maxlinear.com• Rev 4.0.2
ST16C554 / ST16C554D / ST68C554
Data Sheet
2.97V to 5.5V Quad UARTs with 16-Byte FIFO
General Description
The ST16C554, ST16C554D and ST68C554 are each quad
Universal Asynchronous Receivers and Transmitters
(UARTs) with 16 bytes of transmit and receive FIFOs,
selectable receive FIFO trigger levels, and data rates of up to
1.5Mbps. Each UART has a set of registers that provide the
user with operating status and control, receiver error
indications, and modem serial interface controls. An internal
loopback capability allows onboard diagnostics. The
ST16C554 is available in a 64-pin LQFP package, the
ST16C554D is available in both a 64-pin LQFP and a 68-pin
PLCC package, and the ST68C554 is available in a 68-pin
PLCC package. The 64-pin package only offers the 16 mode
interface, but the 68-pin package offers an additional 68
mode interface which allows easy integration with Motorola
processors. The ST16C554CQ64 (64-pin) offers three-state
interrupt output while the ST16C554DCQ64 provides
continuous interrupt output. The ST16C554 and ST16C554D
combine the package interface modes of the 16C554 and
68C554 on a single integrated chip.
Ordering Information - page 32
Features
Pin-to-pin compatible with the industry standard
ST16C454, ST68C454, ST68C554, TI’s TL16C554A and
Philips’ SC16C554B
Intel or Motorola data bus interface select
Four independent UART channels
 Register set compatible to 16C550
 Data rates of up to 1.5Mbps at 5V
 Data rates of up to 500kbps at 3.3V
 16 byte transmit FIFO
 16 byte receive FIFO with error tags
 4 selectable RX FIFO trigger levels
 Full modem interface
2.97V to 5.5V supply operation
Crystal oscillator or external clock input
Applications
Portable appliances
Telecommunication network routers
Ethernet network routers
Cellular data devices
Factory automation and process controls
Block Diagram
Figure 1: ST16C554 Block Diagram
XTAL1
XTAL2
Crystal Osc /Buffer
Data Bus
Interface
UART Channel A
16 Byte TX FIFO
16 Byte RX FIFO
BRG
IR
ENDEC
TX & RX
UART
Regs
2.97 V to 5.5 V VCC
GND
TXB, RXB, IRTXB, DTRB#,
DSRB#, RTSB#, CTSB#,
CDB#, RIB#
UART Channel B
(same as Channel A)
A2:A0
D7:D0
CSA#
16/68#
CSB#
INTA
INTB
IOW#
IOR#
Reset
INTSEL
TXRDY# A-D
RXRDY# A-D
UART Channel C
(same as Channel A)
TXA, RXA, IRTXA, DTRA#,
DSRA#, RTSA#, CTSA#,
CDA#, RIA#
TXC, RXC, IRTXC, DTRC#,
DSRC#, RTSC#, CTSC#,
CDC #, RIC#
UART Channel D
(same as Channel A)
TXD, RXD, IRTXD, DTRD#,
DSRD#, RTSD#, CTSD#,
CDD #, RID#
CSC#
CSD#
INTC
INTD
3.3.0 August 2004 Added Revision History and Device Status. 3.3.1 August 2005 Updated the 1.4mm-thick Quad Flat Pack package description from "TQFP" to "LQFP" to be 4.0.0 April 2006 New datasheet format. Changed active low signal designator from "-” in front of signal name 4.0.1 June 2006 Corrected Part Numbers in Ordering Information. 4.0.2 9/4/19 Update to MaxLinear format. Update Ordering Information and moved to end. Correct pin
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Revision History
9/4/19 Rev 4.0.2 ii
Revision History
Document No. Release Date Change Description
3.3.0 August 2004 Added Revision History and Device Status.
3.3.1 August 2005 Updated the 1.4mm-thick Quad Flat Pack package description from "TQFP" to "LQFP" to be
consistent with JEDEC and Industry norms.
4.0.0 April 2006 New datasheet format. Changed active low signal designator from "-" in front of signal name
to "#" after signal name. Updated AC Electrical Characteristics.
4.0.1 June 2006 Corrected Part Numbers in Ordering Information.
4.0.2 9/4/19 Update to MaxLinear format. Update Ordering Information and moved to end. Correct pin
configuration with selectable 16/68# pin from ST16C554 to ST16C554D.
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UARTs with 16-Byte FIFO Data Sheet Table of Contents
9/4/19 Rev 4.0.2 iii
Table of Contents
General Description............................................................................................................................................. i
Features............................................................................................................................................................... i
Applications ......................................................................................................................................................... i
Block Diagram...................................................................................................................................................... i
1.0 Pin Information ............................................................................................................................................. 1
1.1 Pin Descriptions ......................................................................................................................................................2
2.0 Product Description ..................................................................................................................................... 5
2.1 Enhanced FIFO ...................................................................................................................................................... 5
2.2 Intel or Motorola Data Bus Interface....................................................................................................................... 5
2.3 Data Rate ............................................................................................................................................................... 5
2.4 Enhanced Features ................................................................................................................................................ 5
3.0 Functional Descriptions............................................................................................................................... 6
3.1 CPU Interface..........................................................................................................................................................6
3.2 Device Reset .......................................................................................................................................................... 7
3.3 Channel Selection .................................................................................................................................................. 7
3.4 Internal Registers of Channels A - D...................................................................................................................... 7
3.5 INT Outputs for Channels A - D ............................................................................................................................. 7
3.6 DMA Mode ..............................................................................................................................................................8
3.7 Crystal Oscillator or External Clock Input................................................................................................................8
3.8 Programmable Baud Rate Generator..................................................................................................................... 9
3.9 Transmitter ............................................................................................................................................................10
3.9.1 Transmit Holding Register (THR) - Write Only ..........................................................................................10
3.9.2 Transmitter Operation in Non-FIFO Mode.................................................................................................10
3.9.3 Transmitter Operation in FIFO Mode ........................................................................................................10
3.10 Receiver ............................................................................................................................................................. 10
3.10.1 Receive Holding Register (RHR) - Read Only ........................................................................................11
3.11 Internal Loopback................................................................................................................................................12
4.0 UART Internal Registers ............................................................................................................................ 13
5.0 Internal Register Descriptions................................................................................................................... 15
5.1 Receive Holding Register (RHR) - Read-Only ..................................................................................................... 15
5.2 Transmit Holding Register (THR) - Write-Only..................................................................................................... 15
5.3 Interrupt Enable Register (IER) - Read and Write................................................................................................ 15
5.3.1 IER Versus Receive FIFO Interrupt Mode Operation................................................................................15
5.3.2 IER Versus Receive and Transmit FIFO Polled Mode Operation .............................................................15
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UARTs with 16-Byte FIFO Data Sheet Table of Contents
9/4/19 Rev 4.0.2 iv
5.4 Interrupt Status Register (ISR) ............................................................................................................................. 16
5.4.1 Interrupt Generation ..................................................................................................................................16
5.4.2 Interrupt Clearing.......................................................................................................................................16
5.5 FIFO Control Register (FCR) - Write-Only ............................................................................................................17
5.6 Line Control Register (LCR) - Read and Write..................................................................................................... 17
5.7 Modem Control Register (MCR) or General Purpose Output Control - Read and Write ...................................... 18
5.8 Line Status Register (LSR) - Read and Write....................................................................................................... 19
5.9 Modem Status Register (MSR) - Read and Write .................................................................................................20
5.10 Scratch Pad Register (SPR) - Read and Write................................................................................................... 20
5.11 Baud Rate Generator Registers (DLL and DLM) - Read and Write ................................................................... 21
6.0 Specifications ............................................................................................................................................. 22
6.1 Absolute Maximum Ratings...................................................................................................................................22
6.2 Electrical Characteristics .......................................................................................................................................22
6.2.1 DC Electrical Characteristics.....................................................................................................................22
6.2.2 AC Electrical Characteristics .....................................................................................................................23
7.0 Mechanical Dimensions............................................................................................................................. 30
7.1 LQFP64 .................................................................................................................................................................30
7.2 PLCC68.................................................................................................................................................................31
8.0 Ordering Information.................................................................................................................................. 32
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UARTs with 16-Byte FIFO Data Sheet List of Figures
9/4/19 Rev 4.0.2 v
List of Figures
Figure 1: ST16C554 Block Diagram ...................................................................................................................... i
Figure 2: PLCC68 Pinout, Intel Mode ................................................................................................................... 1
Figure 3: PLCC68 Pinout, Motorola Mode............................................................................................................ 1
Figure 4: LQFP64 Pinout, Intel Mode Only........................................................................................................... 1
Figure 5: PLCC68 Pinout, Motorola Mode Only ................................................................................................... 1
Figure 6: ST16C554D Typical Intel and Motorola Data Bus Interconnections ..................................................... 6
Figure 7: Typical Crystal Connections .................................................................................................................. 8
Figure 8: Baud Rate Generator ............................................................................................................................ 9
Figure 9: Transmitter Operation in Non-FIFO Mode........................................................................................... 10
Figure 10: Transmitter Operation in FIFO Mode................................................................................................. 10
Figure 11: Receiver Operation in Non-FIFO Mode............................................................................................. 11
Figure 12: Receiver Operation in FIFO Mode..................................................................................................... 11
Figure 13: Internal Loopback in Channels A and B ............................................................................................ 12
Figure 14: Clock Timing...................................................................................................................................... 24
Figure 15: Modem Input and Output Timing for Channels A - D ........................................................................ 24
Figure 16: 16 Mode (Intel) Data Bus Read Timing for Channels A - D............................................................... 25
Figure 17: 16 Mode (Intel) Data Bus Write Timing for Channels A - D............................................................... 25
Figure 18: 68 Mode (Motorola) Data Bus Read Timing for Channels A - D ....................................................... 26
Figure 19: 68 Mode (Motorola) Data Bus Write Timing for Channels A - D........................................................ 26
Figure 20: Receive Ready and Interrupt Timing (Non-FIFO Mode) for Channels A - D ..................................... 27
Figure 21: Transmit Ready and Interrupt Timing (Non-FIFO Mode) for Channels A - D .................................... 27
Figure 22: Receive Ready and Interrupt Timing (FIFO Mode, DMA Disabled) for Channels A - D.................... 28
Figure 23: Receive Ready and Interrupt Timing (FIFO Mode, DMA Enabled) for Channels A - D..................... 28
Figure 24: Transmit Ready and Interrupt Timing (FIFO Mode, DMA Disabled) for Channels A - D................... 29
Figure 25: Transmit Ready and Interrupt Timing (FIFO Mode, DMA Enabled) for Channels A - D.................... 29
Figure 26: Mechanical Dimension, LQFP64 (10 x 10 x 1.4mm Low-Profile Quad Flat Pack) ............................ 30
Figure 27: Mechanical Dimensions, PLCC68 (Plastic Leaded Chip Carrier)...................................................... 31
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UARTs with 16-Byte FIFO Data Sheet List of Tables
9/4/19 Rev 4.0.2 vi
List of Tables
Table 1: ST16C554D Pin Descriptions................................................................................................................. 2
Table 2: Channel A - D Select in 16 Mode ........................................................................................................... 7
Table 3: Channel A - D Select in 68 Mode ........................................................................................................... 7
Table 4: INT Pin Operation for Channel A - D Transmitters ................................................................................. 7
Table 5: INT Pin Operation for Channel A - D Receivers ..................................................................................... 8
Table 6: TXRDY# and RXRDY# Outputs in FIFO and DMA Mode for Channels A - D........................................ 8
Table 7: Typical Data Rates with a 14.7456MHz Crystal or External Clock......................................................... 9
Table 8: Internal Registers of UART Channels A and B..................................................................................... 13
Table 9: Internal Register Descriptions............................................................................................................... 14
Table 10: Interrupt Source and Priority Level ..................................................................................................... 16
Table 11: Receive FIFO Trigger Level Selection................................................................................................ 17
Table 12: TX and RX Word Length..................................................................................................................... 17
Table 13: TX and RX Stop-Bit Length ................................................................................................................ 17
Table 14: Parity Selection................................................................................................................................... 18
Table 15: INT Output Modes .............................................................................................................................. 19
Table 16: UART Reset Conditions for Channels A - D ....................................................................................... 21
Table 17: Absolute Maximum Ratings................................................................................................................ 22
Table 18: Typical Package Thermal Resistance Data........................................................................................ 22
Table 19: Electrical Characteristics .................................................................................................................... 22
Table 20: AC Electrical Characteristics .............................................................................................................. 23
Table 21: Ordering Information........................................................................................................................... 32
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ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UARTs with 16-Byte FIFO Data Sheet Pin Information
9/4/19 Rev 4.0.2 1
1.0 Pin Information
1.1 Pin Configurations
Figure 2: PLCC68 Pinout, Intel Mode Figure 3: PLCC68 Pinout, Motorola Mode
D
D
Figure 4: LQFP64 Pinout, Intel Mode Only Figure 5: PLCC68 Pinout, Motorola Mode Only
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
DSRA#
CTSA#
DTRA#
VCC
RTSA#
INTA
CSA#
TXA
IOW#
TXB
CSB#
INTB
RTSB#
GND
DTRB#
CTSB#
DSRB#
CDB#
RIB#
RXB
VCC
A2
A1
A0
XTAL1
XTAL2
RESET
GND
RXC
RIC#
CDC#
DSRC#
DSRD#
CTSD#
DTRD#
GND
RTSD#
INTD
CSD#
TXD
IOR#
TXC
CSC#
INTC
RTSC#
VCC
DTRC#
CTSC#
CDA#
RIA#
RXA
GND
D7
D6
D5
D4
D3
D2
D1
D0
VCC
RXD
RID#
CDD#
ST16C554/554D
64-pin LQFP
Intel Mode Only
9
8
7
6
5
4
3
2
1
68
67
66
65
64
63
62
63
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
DSRA#
CTSA#
DTRA#
VCC
RTSA#
IRQ#
CS#
TXA
R/W#
TXB
A3
N.C.
RTSB#
GND
DTRB#
CTSB#
DSRB#
CDB#
RIB#
RXB
VCC
GND
A2
A1
A0
XTAL1
XTAL2
RESET
RXRDY#
TXRDY#
GND
RXC
RIC#
CDC#
DSRD#
CTSD#
DTRD#
GND
RTSD#
N.C.
N.C.
TXD
N.C.
TXC
A4
N.C.
RTSC#
VCC
DTRC#
CTSC#
DSRC#
CDA#
RIA#
RXA
GND
D7
D6
D5
D4
D3
D2
D1
D0
GND
VCC
RXD
RID#
CDD#
ST68C554
68-pin PLCC
Motorola Mode Only
Data Bus Interfaoe A2 22 32 A1 23 33 A0 24 34 D7 60 5 D6 59 4 D5 58 3 D4 57 2 D3 56 1 D2 55 68 D1 54 67 D0 53 66 When the 16/68:: pin is HIGH, the Intel bus interface is selected and this input When the 16/68:: pin is HIGH, it selects the Intel bus interface and this input When the 16/68:: pin is HIGH, this input is chip selectA (active low) to enable When the 16/68:: pin is HIGH, this input is chip select B (active low) ta enable When the 16/68:: pin is HIGH, this input is chip select C (active low) ta enable When the 16/68:: pin is HIGH, this input is chip select D (active low) ta enable
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Pin Descriptions
9/4/19 Rev 4.0.2 2
1.2 Pin Descriptions
Table 1: Pin Descriptions
Name LQFP64 PLCC68 Type Description
Data Bus Interface
A2 22 32
IAddress data lines [2:0]. These 3 address lines select one of the internal registers
in UART channel A - D during a data bus transaction.
A1 23 33
A0 24 34
D7 60 5
I/O Data bus lines [7:0] (bidirectional).
D6 59 4
D5 58 3
D4 57 2
D3 56 1
D2 55 68
D1 54 67
D0 53 66
IOR#
(VCC) 40 52 I
When the 16/68# pin is HIGH, the Intel bus interface is selected and this input
becomes a read strobe (active low). The falling edge instigates an internal read
cycle and retrieves the data byte from an internal register pointed to by the
address lines [A2:A0], puts the data byte on the data bus to allow the host
processor to read it on the rising edge.
When the 16/68# pin is LOW, the Motorola bus interface is selected and this input
is not used and should be connected to VCC.
IOW#
(R/W#) 9 18 I
When the 16/68# pin is HIGH, it selects the Intel bus interface and this input
becomes a write strobe (active low). The falling edge instigates the internal write
cycle and the rising edge transfers the data byte on the data bus to an internal
register pointed to by the address lines.
When the 16/68# pin is LOW, the Motorola bus interface is selected and this input
becomes read (HIGH) and write (LOW) signal.
CSA#
(CS#) 7 16 I
When the 16/68# pin is HIGH, this input is chip select A (active low) to enable
channel A in the device.
When the 16/68# pin is LOW, this input becomes the chip select (active low) for
the Motorola bus interface.
CSB#
(A3) 11 20 I
When the 16/68# pin is HIGH, this input is chip select B (active low) to enable
channel B in the device.
When the 16/68# pin is LOW, this input becomes address line A3 which is used for
channel selection in the Motorola bus interface.
CSC#
(A4) 38 50 I
When the 16/68# pin is HIGH, this input is chip select C (active low) to enable
channel C in the device.
When the 16/68# pin is LOW, this input becomes address line A4 which is used for
channel selection in the Motorola bus interface.
CSD#
(VCC) 42 54 I
When the 16/68# pin is HIGH, this input is chip select D (active low) to enable
channel D in the device.
When the 16/68# pin is LOW, this input is not used and should be connected to
VCC.
LQFP64 PLCCBB WW Description When the 16/6813 pin is HIGH for Intel bus interface, this output becomes the | NTB | NTC INTD When the 16/6813 pin is HIGH for Intel bus interface, these outputs become the Interrupt Select (active high, input with internal pull-down), When the 16/6813 pin is HIGH for Intel bus interf n be used in conlunction with MCR bit»3 to enable or disable ns or ovem MCR bit-3 and enable the interrupt outputs, In e enabled continuously when this pin is HIGH. MCR bit- bles the interrup output pins. In this mode, MCR bit-3 is set to he continuous output. See MCR[3] INT Output Enable des Thi 2n must be LOW in the Motorola bus interface mode, Transmitter Ready (active low). This output is a logically ANDed status of Receiver Ready (active low). This output is a logically ANDed status of Modem or Serial IIO Interface TXA a 17 TXB 1o 19 TXC '39 51 TXD 41 53 RXA '62 7 RXB 20 29 RXC '29 41 RXD 51 63 RTSA# '5 14 RTSB# 13 22 RTSC# '36 48 RTSD# 44 56 CTSA# '2 11 crsrm 1e 25 CTSC# '33 45 crsw 47 59
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Pin Descriptions
9/4/19 Rev 4.0.2 3
INTA
(IRQ#) 6 15 O
(OD)
When the 16/68# pin is HIGH for Intel bus interface, this output becomes the
channel A interrupt output. The output state is defined by the user and through the
software setting of MCR[3]. INTA is set to the active mode when MCR[3] is set to a
logic 1. INTA is set to the three state mode when MCR[3] is set to a logic 0
(default). See MCR[3]: INT Output Enable.
When the 16/68# pin is LOW for Motorola bus interface, this output becomes the
device interrupt output (active low, open drain). An external pull-up resistor is
required for proper operation.
INTB
(N.C.) 12 21
O
When the 16/68# pin is HIGH for Intel bus interface, these outputs become the
interrupt outputs for channels B, C, and D. The output state is defined by the user
through the software setting of MCR[3]. The interrupt outputs are set to the active
mode when MCR[3] is set to a logic 1 and are set to the three state mode when
MCR[3] is set to a logic 0 (default). See MCR[3]: INT Output Enable.
When 16/68# pin is LOW for Motorola bus interface, these outputs are unused and
will stay at logic zero level. Leave these outputs unconnected.
INTC
(N.C.) 37 49
INTD
(N.C.) 43 55
INTSEL - 65 I
Interrupt Select (active high, input with internal pull-down).
When the 16/68# pin is HIGH for Intel bus interface, this pin can be used in
conjunction with MCR bit-3 to enable or disable the INT A - D pins or override
MCR bit-3 and enable the interrupt outputs. Interrupt outputs are enabled
continuously when this pin is HIGH. MCR bit-3 enables and disables the interrupt
output pins. In this mode, MCR bit-3 is set to a logic 1 to enable the continuous
output. See MCR[3]: INT Output Enable description for full detail. This pin must
be LOW in the Motorola bus interface mode. For the 64 pin packages, this pin is
bonded to VCC internally in the ST16C554DCQ64-F so the INT outputs operate in
the continuous interrupt mode. This pin is bonded to GND internally in the
ST16C554CQ64 and therefore requires setting MCR bit-3 for enabling the
interrupt output pins.
TXRDY# - 39 O Transmitter Ready (active low). This output is a logically ANDed status of
TXRDY# A - D. See Table 6. If this output is unused, leave it unconnected.
RXRDY# - 38 O Receiver Ready (active low). This output is a logically ANDed status of
RXRDY# A - D. See Table 6. If this output is unused, leave it unconnected.
Modem or Serial I/O Interface
TXA 8 17
OUART channels A - D transmit data and infrared transmit data. In this mode, the
TX signal will be HIGH during reset, or idle (no data).
TXB 10 19
TXC 39 51
TXD 41 53
RXA 62 7
I UART channel A - D receive data. Normal receive data input must idle HIGH.
RXB 20 29
RXC 29 41
RXD 51 63
RTSA# 5 14
OUART channels A - D Request-to-Send (active low) or general purpose output. If
these outputs are not used, leave them unconnected.
RTSB# 13 22
RTSC# 36 48
RTSD# 44 56
CTSA# 2 11
IUART channels A - D Clear-to-Send (active low) or general purpose input. These
inputs should be connected to VCC when not used.
CTSB# 16 25
CTSC# 33 45
CTSD# 47 59
Table 1: (Continued) Pin Descriptions
Name LQFP64 PLCC68 Type Description
DTRA# 3 DTREW 1 5 DTRCI? 34 DTRD# 46 DSRAI? 1 DSREW 1 7 DSRCI? 32 DSRDI? 48 (IBM? 64 CD3# 1 3 CD01? 31 CDD# 49 R|A# 63 RI Bit 1 9 RIC?‘ 30 R|D# 50 Ancillary Signals XTAL1 25 35 | Crystal or external clock input. XTAL2 26 36 0 Crystal or bquered clock output. Intel or Motorola bus select (input with internal pull-up). When the 16/68:: pin is HIGH for Intel bus interface, this input becomes the Reset 4. 21, 13, 30, 14. 28, 6, 23, MC. - - No connection. These pins are not used in either the Intel or Motorola bus modes.
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Pin Descriptions
9/4/19 Rev 4.0.2 4
Pin type: I = Input, O = Output, I/O = Input / Output, OD = Output, Open Drain.
DTRA# 3 12
OUART channels A - D Data-Terminal-Ready (active low) or general purpose
output. If these outputs are not used, leave them unconnected.
DTRB# 15 24
DTRC# 34 46
DTRD# 46 58
DSRA# 1 10
I
UART channels A - D Data-Set-Ready (active low) or general purpose input. This
input should be connected to VCC when not used. This input has no effect on the
UART.
DSRB# 17 26
DSRC# 32 44
DSRD# 48 60
CDA# 64 9
I
UART channels A-D Carrier-Detect (active low) or general purpose input. This
input should be connected to VCC when not used. This input has no effect on the
UART.
CDB# 18 27
CDC# 31 43
CDD# 49 61
RIA# 63 8
I
UART channels A-D Ring-Indicator (active low) or general purpose input. This
input should be connected to VCC when not used. This input has no effect on the
UART.
RIB# 19 28
RIC# 30 42
RID# 50 62
Ancillary Signals
XTAL1 25 35 I Crystal or external clock input.
XTAL2 26 36 O Crystal or buffered clock output.
16/68# - 31 I
Intel or Motorola bus select (input with internal pull-up).
When the 16/68# pin is HIGH for 16 or Intel Mode, the device will operate in the
Intel bus type of interface.
When the 16/68# pin is LOW for 68 or Motorola Mode, the device will operate in
the Motorola bus type of interface.
Motorola bus interface is not available on the 64 pin package.
RESET
(RESET#) 27 37 I
When the 16/68# pin is HIGH for Intel bus interface, this input becomes the Reset
pin (active high). In this case, a 40ns minimum HIGH pulse on this pin will reset
the internal registers and all outputs. The UART transmitter output will be held
HIGH, the receiver input will be ignored, and outputs are reset during the reset
period (Table 16).
When the 16/68# pin is at LOW for Motorola bus interface, this input becomes the
Reset# pin (active low). This pin functions similarly, but instead of a HIGH pulse, a
40ns minimum LOW pulse will reset the internal registers and outputs.
Motorola bus interface is not available on the 64 pin package.
VCC 4, 21,
35, 52
13, 30,
47, 64 Pwr 2.97V to 5.5V power supply.
GND 14, 28,
45, 61
6, 23,
40, 57 Pwr Power supply common, ground.
N.C. - - No connection. These pins are not used in either the Intel or Motorola bus modes.
Table 1: (Continued) Pin Descriptions
Name LQFP64 PLCC68 Type Description
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Product Description
9/4/19 Rev 4.0.2 5
2.0 Product Description
The ST16C554 integrates the functions of 4 enhanced
16C550 Universal Asynchronous Receiver and
Transmitters (UARTs). Each UART is independently
controlled and has its own set of device configuration
registers. The configuration registers set is 16550 UART
compatible for control, status, and data transfer.
Additionally, each UART channel has 16 bytes of transmit
and receive FIFOs, a programmable baud rate generator
and data rate up to 1.5Mbps at 5V. The ST16C554 can
operate from 2.97 to 5.5 volts. The ST16C554 is fabricated
with an advanced CMOS process.
2.1 Enhanced FIFO
The ST16C554 QUART provides a solution that supports
16 bytes of transmit and receive FIFO memory, instead of
one byte in the ST16C454. The ST16C554 is designed to
work with high performance data communication systems
that require fast data processing time. Increased
performance is realized in the ST16C554 by the larger
transmit and receive FIFOs and receiver FIFO trigger level
control. This allows the external processor to handle more
networking tasks within a given time. This increases the
service interval giving the external CPU additional time for
other applications and reducing the overall UART interrupt
servicing time.
2.2 Intel or Motorola Data Bus
Interface
The ST16C554 provides a single host interface for all 4
UARTs and supports Intel or Motorola microprocessor
(CPU) data bus interfaces. The Intel bus compatible
interface allows direct interconnect to Intel compatible type
of CPUs using IOR#, IOW# and CSA#, CSB#, CSC# and
CSD# inputs for data bus operation. The Motorola bus
compatible interface instead uses the R/W#, CS#, A3 and
A4 signals for data bus transactions. Few data bus
interface signals change their functions depending on the
user’s selection, see pin description for details. The Intel or
Motorola bus interface selection is made through the
16/68# (pin 31 of the PLCC package).
2.3 Data Rate
The ST16C554 is capable of operation up to 1.5 Mbps at
5V. The device can operate at 5V with a crystal or external
clock of up to 24MHz. With a typical crystal of 14.7456MHz
and through a software option, the user can set the
sampling rate for data rates of up to 921.6kbps.
2.4 Enhanced Features
The rich feature set of the ST16C554 is available through
the internal registers. Selectable receive FIFO trigger
levels, programmable baud rates, infrared encoder and
decoder interface, and modem interface controls are all
standard features. In the 16 mode, INTSEL and MCR bit-3
can be configured to provide a software controlled or
continuous interrupt capability. For backward compatibility
to the ST16C554, the 64-pin LQFP does not have the
INTSEL pin. Instead, the ST16C554DIQ and
ST16C554DCQ operate in the continuous interrupt enable
mode by internally bonding INTSEL to VCC. The
ST16C554CQ operates in conjunction with MCR bit-3 by
internally bonding INTSEL to GND.
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Functional Descriptions
9/4/19 Rev 4.0.2 6
3.0 Functional Descriptions
3.1 CPU Interface
The CPU interface is 8 data bits wide with 3 address lines
and control signals to execute data bus read and write
transactions. The ST16C554 data interface supports the
Intel compatible types of CPUs and it is compatible to the
industry standard 16C550 UART. No clock (oscillator nor
external clock) is required for a data bus transaction. Each
bus cycle is asynchronous using CS# A - D, IOR# and
IOW# or CS#, R/W#, A4 and A3 inputs. All four UART
channels share the same data bus for host operations. A
typical data bus interconnection for Intel and Motorola
Modes is shown in Figure 6.
Figure 6: ST16C554D Typical Intel and Motorola Data Bus Interconnections
VCC
VCC
DSRA#
CTSA#
RTSA#
DTRA#
RXA
TXA
RIA#
CDA#
GND
A0
A1
A2
UART_CSA#
UART_CSB#
IOR#
IOW#
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
A2
CSA#
CSB#
D0
D1
D2
D3
D4
D5
D6
D7
IOR#
IOW#
UART
Channel A
UART
Channel B
UART_INTB
UART_INTA
INTB
INTA
UART_RESET RESET
Serial Interface of
RS-232
Serial Interface of
RS-232
Intel Data Bus (16 Mode) Interconnections
UART
Channel C
UART
Channel D
Simil ar
to Ch A
Simil ar
to Ch A
Simil ar
to Ch A
UART_INTD
UART_INTC
INTD
INTC
UART_CSC#
UART_CSD#
CSC#
CSD#
VCC 16/68#
VCC
VCC
GND
A0
A1
A2
UART_CS#
A3
R/W#
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
A2
CSA#
CSB#
D0
D1
D2
D3
D4
D5
D6
D7
IOR#
IOW#
UART_IRQ#
INTB
INTA
RESET#
Serial Interface of
RS-232
Serial Interface of
RS-232
Motorola Data Bus (68 Mode) Interconnections
VCC
UART_RESET#
(no connect)
DSRA#
CTSA#
RTSA#
DTRA#
RXA
TXA
RIA#
CDA#
UART
Channel A
UART
Channel B
UART
Channel C
Similar
to Ch A
Similar
to Ch A
Similar
to Ch A
INTC
(no connect)
INTD
(no connect)
A4 CSC#
CSD#
VCC
16/68#
UART
Channel D
VCC
UART de-selecled Channel A selected Channel B selected Channel C selected Channel D selected 0000.. _._.00>< _.o_.0x="" uart="" deselected="" channel="" a="" selected="" channel="" b="" selected="" channel="" c="" selected="" channel="" d="" selected="" 0—-—-_.0_n="" o—x—xoaa="" o—xoaaa="" oo—xaaa="" channelsa-="" d="" selected="">
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Device Reset
9/4/19 Rev 4.0.2 7
3.2 Device Reset
The RESET input resets the internal registers and the
serial interface outputs in all channels to their default state
(see Table 16). An active high pulse of longer than a 40ns
duration will be required to activate the reset function in the
device. Following a power-on reset or an external reset,
the ST16C554 is software compatible with previous
generation of UARTs, the 16C454 and 16C554.
3.3 Channel Selection
The UART provides the user with the capability to bi-
directionally transfer information between an external CPU
and an external serial communication device. During Intel
Bus Mode (16/68# pin is connected to VCC), a logic 0 on
chip select pins CSA#, CSB#, CSC#, or CSD# allows the
user to select UART channel A, B, C, or D to configure,
send transmit data and unload receive data to and from the
UART. Selecting all four UARTs can be useful during power
up initialization to write to the same internal registers, but
do not attempt to read from all four UARTs simultaneously.
Individual channel select functions are shown in Table 2.
During Motorola Bus Mode (16/68# pin is connected to
GND), the package interface pins are configured for
connection with Motorola, and other popular
microprocessor bus types. In this mode, the ST16C554
decodes two additional addresses, A3 and A4, to select
one of the four UART ports. The A3 and A4 address
decode function is used only in the Motorola Bus Mode.
See Table 3.
3.4 Internal Registers of Channels A - D
Each UART channel in the ST16C554 has a set of
enhanced registers for controlling, monitoring and data
loading and unloading. The configuration register set is
compatible to those already available in the standard single
16C550. These registers function as data holding registers
(THR / RHR), interrupt status and control registers (ISR /
IER), a FIFO control register (FCR), receive line status and
control registers (LSR / LCR), modem status and control
registers (MSR / MCR), programmable data rate (clock)
divisor registers (DLL / DLM), and a user accessible
scratchpad register (SPR). All the register functions are
discussed in full detail later in UART Internal Registers.
3.5 INT Outputs for Channels A - D
The interrupt outputs change according to the operating
mode and enhanced features setup. Table 4 and Table 5
summarize the operating behavior for the transmitter and
receiver. Also see Figure 20 through Figure 25.
Table 2: Channel A - D Select in 16 Mode
CSA# CSB# CSC# CSD# Function
1 1 1 1 UART de-selected
0 1 1 1 Channel A selected
1 0 1 1 Channel B selected
1 1 0 1 Channel C selected
1 1 1 0 Channel D selected
0 0 0 0 Channels A - D selected
Table 3: Channel A - D Select in 68 Mode
CS# A4 A3 Function
1 X X UART de-selected
0 0 0 Channel A selected
0 0 1 Channel B selected
0 1 0 Channel C selected
0 1 1 Channel D selected
Table 4: INT Pin Operation for Channel A - D Transmitters
INT Pin FCR Bit-0 = 0
(FIFO Disabled)
FCR Bit-0 = 1 (FIFO Enabled)
FCR Bit-3 = 0
(DMA Mode Disabled)
FCR Bit-3 = 1
(DMA Mode Enabled)
LOW A byte in THR FIFO above trigger level FIFO above trigger level
HIGH THR empty FIFO below trigger level or FIFO empty FIFO below trigger level or FIFO empty
HIGH 1 byte FIFO above trigger level FIFO above trigger level LOW 1 byte At least 1 byte in FIFO HIGH to LOW transition when FIFO reachesthe trigger LOW THR empty FIFO empty FIFO has at least 1 empty location HIGH Byte in THR At Iea5t1 byte in FIFO FIFO is full The ST160554 includes an on-chip oscillator (XTAL1 and XTAL2) to produce a clock for both UART sections in the device. The QPLJ data bgg gggg ngt rfiuim this gogk fgr 1| 1
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet DMA Mode
9/4/19 Rev 4.0.2 8
3.6 DMA Mode
The device does not support direct memory access. The
DMA Mode (a legacy term) in this document does not
mean “direct memory access”, but refers to data block
transfer operation. The DMA mode affects the state of the
RXRDY# A - D and TXRDY# A - D output pins. The
transmit and receive FIFO trigger levels provide additional
flexibility to the user for block mode operation. The LSR bits
5-6 provide an indication when the transmitter is empty or
has empty locations for more data. The user can optionally
operate the transmit and receive FIFO in the DMA mode
(FCR bit-3 = 1). When the transmit and receive FIFOs are
enabled and the DMA mode is disabled (FCR bit-3 = 0), the
ST16C554 is placed in Single-Character Mode for data
transmit or receive operation. When DMA Mode is enabled
(FCR bit-3 = 1), the user takes advantage of block mode
operation by loading or unloading the FIFO in a block
sequence determined by the programmed trigger level. The
following table shows their behavior. Also see Figure 20
through Figure 25.
3.7 Crystal Oscillator or External Clock Input
The ST16C554 includes an on-chip oscillator (XTAL1 and
XTAL2) to produce a clock for both UART sections in the
device. The CPU data bus does not require this clock for
bus operation. The crystal oscillator provides a system
clock to the Baud Rate Generators (BRG) section found in
each of the UARTs. XTAL1 is the input to the oscillator or
external clock buffer input with XTAL2 pin being the output.
For programming details, see Programmable Baud Rate
Generator.
The on-chip oscillator is designed to use an industry
standard microprocessor crystal (parallel resonant,
fundamental frequency with 10 - 22pF capacitance load,
ESR of 20 - 120Ω and 100ppm frequency tolerance)
connected externally between the XTAL1 and XTAL2 pins.
Typical oscillator connections are shown in Figure 7.
Alternatively, an external clock can be connected to the
XTAL1 pin to clock the internal baud rate generator for
standard or custom rates. For further reading on oscillator
circuit please see Application Note DAN108 on
MaxLinear’s web site.
Figure 7: Typical Crystal Connections
Table 5: INT Pin Operation for Channel A - D Receivers
INT Pin FCR Bit-0 = 0
(FIFO Disabled)
FCR Bit-0 = 1 (FIFO Enabled)
FCR Bit-3 = 0
(DMA Mode Disabled)
FCR Bit-3 = 1
(DMA Mode Enabled)
LOW No data FIFO below trigger level FIFO below trigger level
HIGH 1 byte FIFO above trigger level FIFO above trigger level
Table 6: TXRDY# and RXRDY# Outputs in FIFO and DMA Mode for Channels A - D
Pins FCR Bit-0 = 0
(FIFO Disabled)
FCR Bit-0 = 1 (FIFO Enabled)
FCR Bit-3 = 0
(DMA Mode Disabled)
FCR Bit-3 = 1
(DMA Mode Enabled)
RXRDY#
LOW 1 byte At least 1 byte in FIFO HIGH to LOW transition when FIFO reaches the trigger
level, or timeout occurs.
LOW to HIGH transition when FIFO empties.
HIGH No data FIFO empty
TXRDY# LOW THR empty FIFO empty FIFO has at least 1 empty location
HIGH Byte in THR At least 1 byte in FIFO FIFO is full
H
ST16C554 / ST16C554D / ST68C554 Data Sheet Programmable Baud Rate Generator
9/4/19 Rev 4.0.2 9
3.8 Programmable Baud Rate Generator
Each UART has its own Baud Rate Generator (BRG) for
the transmitter and receiver. The BRG further divides this
clock by a programmable divisor between 1 and (216 - 1) to
obtain a 16X sampling rate clock of the serial data rate. The
sampling rate clock is used by the transmitter for data bit
shifting and the receiver for data sampling. The BRG
divisor is unknown (DLL = 0xXX and DLM = 0xXX) and
should be initialized after power up. Programming the Baud
Rate Generator Registers DLL and DLM provide the
capability for selecting the operating data rate. Table 7
shows the standard data rates available with a
14.7456MHz crystal or external clock.
Figure 8: Baud Rate Generator
Table 7: Typical Data Rates with a 14.7456MHz Crystal or External Clock
Output Data Rate
MCR Bit-7=1
Output Data Rate
MCR Bit-7=0
(Default)
Divisor for 16x
Clock (Decimal)
Divisor for 16x
Clock (HEX)
DLM Program
Value (HEX)
DLL Program
Value (HEX)
Data Rate
Error (%)
100 400 2304 900 09 00 0
600 2400 384 180 01 80 0
1200 4800 192 C0 00 C0 0
2400 9600 96 60 00 60 0
4800 19.2k 48 30 00 30 0
9600 38.4k 24 18 00 18 0
19.2k 76.8k 12 0C 00 0C 0
38.4k 153.6k 6 06 00 06 0
57.6k 230.4k 4 04 00 04 0
115.2k 460.8k 2 02 00 02 0
230.4k 921.6k 1 01 00 01 0
XTAL1
XTAL2
Crystal
Osc/
Buffer
DLL and DLM
Registers
16 X Sampling
Rate Clock
to Transmitter
and Receiver
To Other
Channels
Programmable Baud
Rate Generator Logic
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Transmitter
9/4/19 Rev 4.0.2 10
3.9 Transmitter
The transmitter section comprises of an 8-bit Transmit Shift
Register (TSR) and 16 bytes of FIFO which includes a
byte-wide Transmit Holding Register (THR). TSR shifts out
every data bit with the 16X internal sampling clock. A bit
time is 16X clock periods. The transmitter sends the start-
bit followed by the number of data bits, inserts the proper
parity-bit if enabled, and adds the stop-bit(s). The status of
the FIFO and TSR are reported in the Line Status Register
(LSR bit-5 and bit-6).
3.9.1 Transmit Holding Register (THR)
- Write Only
The transmit holding register is an 8-bit register providing a
data interface to the host processor. The host writes a
transmit data byte to the THR to be converted into a serial
data stream including start-bit, data bits, parity-bit and stop-
bit(s). The least-significant-bit (bit-0) becomes the first data
bit to go out. The THR is the input register to the transmit
FIFO of 16 bytes when FIFO operation is enabled by FCR
bit-0. Every time a write operation is made to the THR, the
FIFO data pointer is automatically bumped to the next
sequential data location.
3.9.2 Transmitter Operation in Non-FIFO
Mode
The host loads transmit data to THR one character at a
time. The THR empty flag (LSR bit-5) is set when the data
byte is transferred to TSR. The THR flag can generate a
transmit empty interrupt (ISR bit-1) when it is enabled by
IER bit-1. The TSR flag (LSR bit-6) is set when TSR
becomes completely empty.
Figure 9: Transmitter Operation in Non-FIFO Mode
3.9.3 Transmitter Operation in FIFO Mode
The host may fill the transmit FIFO with up to 16 bytes of
transmit data. The THR empty flag (LSR bit-5) is set
whenever the FIFO is empty. The THR empty flag can
generate a transmit empty interrupt (ISR bit-1) when the
FIFO becomes empty. The transmit empty interrupt is
enabled by IER bit-1. The TSR flag (LSR bit-6) is set when
TSR and the FIFO becomes empty.
Figure 10: Transmitter Operation in FIFO Mode
3.10 Receiver
The receiver section contains an 8-bit Receive Shift
Register (RSR) and 16 bytes of FIFO which includes a byte-
wide Receive Holding Register (RHR). The RSR uses the
16X clock for timing. It verifies and validates every bit on the
incoming character in the middle of each data bit. On the
falling edge of a start or false start bit, an internal receiver
counter starts counting at the 16X clock rate. After 8 clocks,
the start bit period should be at the center of the start bit. At
this time the start bit is sampled, and if it is still LOW it is
validated. Evaluating the start bit in this manner prevents
the receiver from assembling a false character. The rest of
the data bits and stop bits are sampled and validated in this
same manner to prevent false framing. If there were any
error(s), they are reported in the LSR register bits 2 - 4.
Upon unloading the receive data byte from RHR, the
receive FIFO pointer is bumped and the error tags are
immediately updated to reflect the status of the data byte in
the RHR register. RHR can generate a receive data ready
interrupt upon receiving a character or delay, until it reaches
the FIFO trigger level. Furthermore, data delivery to the host
is guaranteed by a receive data ready time-out interrupt
when data is not received for 4 word lengths as defined by
LCR[1:0] plus 12 bits time. This is equivalent to 3.7 - 4.6
character times. The RHR interrupt is enabled by IER bit-0.
See Figure 11 and Figure 12.
Transmit
Holding
Register
(THR)
Transmit Shift Register (TSR)
Data
Byte
L
S
B
M
S
B
THR Interrupt (ISR bit-1)
Enabled by IER bit-1
TXNOFIFO1
16X Clock
Transmit Data Shift Register
(TSR)
Transmit
Data Byte THR Interrupt (ISR bit-1)
when the TX FIFO
becomes empty. FIFO is
enabled by FCR bit-0 =1.
Transmit
FIFO
16X Clock
TXFIFO1
4—1-T ‘—‘L—J’
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Receiver
9/4/19 Rev 4.0.2 11
3.10.1 Receive Holding Register (RHR) - Read Only
The Receive Holding Register is an 8-bit register that holds
a receive data byte from the Receive Shift Register. It
provides the receive data interface to the host processor.
The RHR register is part of the receive FIFO of 16 bytes by
11-bit wide; the 3 extra bits are for the 3 error tags to be
reported in LSR register. When the FIFO is enabled by
FCR bit-0, the RHR contains the first data character
received by the FIFO. After the RHR is read, the next
character byte is loaded into the RHR and the errors
associated with the current data byte are immediately
updated in the LSR bits 2 - 4.
Figure 11: Receiver Operation in Non-FIFO Mode
Figure 12: Receiver Operation in FIFO Mode
Receive Data Shift
Register (RSR)
Receive
Data Byte
and Errors RHR Interrupt (ISR bit-2)
Receive Data
Holding Register
(RHR)
RXFIFO1
16X Clock
Receive Data Characters
Data Bit
Validation
Error
Tags in
LSR bits
4:2
Receive D ata Shift
Register (RSR)
RXFIFO1
16X Clock
Error Tags
(16-sets)
Error Tags in
LSR bits 4:2
Receive Data Characters
Data Bit
Valida tion
Receive
Data FIFO
Receive
Data
Receive Data
Byte and Errors
RHR Interrupt (ISR bit-2) program med for
desired FIFO trigger level.
FIFO is Enabled by FCR bit-0=1
Asking for stopping data when data fills above the flow
control trigger level to suspend remote transmitter.
Asking for sending data when data falls below the flow
control trigger level to restart remote transmitter.
16 bytes by 11-bit wide
FIFO
FIFO
Trigger=8
Data falls to
4
Data fills to
14
Example
: - RX FIFO trigger level selected at 8 bytes
(See Note Below)
1 if i L L
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Internal Loopback
9/4/19 Rev 4.0.2 12
3.11 Internal Loopback
The ST16C554 UART provides an internal loopback
capability for system diagnostic purposes. The internal
loopback mode is enabled by setting MCR register bit-4 to
a logic 1. All regular UART functions operate normally.
Figure 13 shows how the modem port signals are re-
configured. Transmit data from the Transmit Shift Register
output is internally routed to the Receive Shift Register
input, allowing the system to receive the same data that it
was sending. The TX pin is held HIGH or at mark condition
while RTS# and DTR# are de-asserted, and CTS#, DSR#
CD# and RI# inputs are ignored.
Important: The RX input must be held HIGH during the
loopback test, else upon exiting the loopback test the
UART may detect and report a false “break” signal.
Figure 13: Internal Loopback in Channels A and B
TX A-D
RX A-D
Modem / General Purpose Control Logic
Internal Data Bus Lines and Control Signals
RTS# A-D
MCR bit-4=1
VCC
VCC
Transmit Shift Register
(THR/FIFO)
Receive Shift Register
(RHR/FIFO)
CTS# A-D
DTR# A-D
DSR# A-D
RI# A-D
CD# A-D
OP1#
OP2#
RTS#
CTS#
DTR#
DSR#
RI#
CD#
VCC
160550 Compatible Registers RHR - Receive Holding Register Read-only THR - Transmit Holding Register Write-only 0 0 0 DLL - Divisor LSB Read and write 0 0 1 DLM - Divisor MSB Read and write 0 0 1 IER - Interrupt Enable Register Read and write ISR - Interrupt Status Register Read-only FCR - FIFO Control Register Write-only 0 1 1 LCR - Line Control Register Read and write 1 0 0 MCR - Modern Control Register Read and write 1 0 1 LSR - Line Status Register Read-only 1 1 0 MSR - Modern Status Register Read-only 1 1 1 SPR - Scratch Pad Register Read and write
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet UART Internal Registers
9/4/19 Rev 4.0.2 13
4.0 UART Internal Registers
Each UART channel in the ST16C554 has its own set of configuration registers selected by address lines A0, A1, and A2
with a specific channel selected (see Table 2 and Table 3). The complete register set is shown in Table 8 and Table 9.
Table 8: Internal Registers of UART Channels A and B
A2, A1, A0 Addresses Register Read and Write Comments
16C550 Compatible Registers
0 0 0 RHR - Receive Holding Register Read-only LCR[7] = 0
THR - Transmit Holding Register Write-only
0 0 0 DLL - Divisor LSB Read and write LCR[7] = 1
0 0 1 DLM - Divisor MSB Read and write
0 0 1 IER - Interrupt Enable Register Read and write
LCR[7] = 0
0 1 0 ISR - Interrupt Status Register Read-only
FCR - FIFO Control Register Write-only
0 1 1 LCR - Line Control Register Read and write
1 0 0 MCR - Modem Control Register Read and write
LCR[7] = 0
1 0 1 LSR - Line Status Register Read-only
1 1 0 MSR - Modem Status Register Read-only
1 1 1 SPR - Scratch Pad Register Read and write
160550 Compatible Registers 0 O O RHR RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 0 O O THR WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 RX INT INT INT INT RX RX DMA TX RX Word Word INT RX CD# Rlit DSR# CTS# Delta Delka Delka Delta 1 1 1 SPR RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 Baud Rate Generator Divisor 0 O O DLL RD I WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 O O 1 DLM RD / WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet UART Internal Registers
9/4/19 Rev 4.0.2 14
Table 9: Internal Register Descriptions
Address
A2 - A0
Register
Name Read / Write Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 Comment
16C550 Compatible Registers
0 0 0 RHR RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
LCR[7] = 0
0 0 0 THR WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
0 0 1 IER RD / WR 0 0 0 0
Modem
Stat.
Int.
Enable
RX
Line
Stat.
Int.
Enable
TX
Empty
Int
Enable
RX
Data
Int.
Enable
0 1 0 ISR RD FIFOs
Enabled
FIFOs
Enabled 0 0
INT
Source
Bit-3
INT
Source
Bit-2
INT
Source
Bit-1
INT
Source
Bit-0
0 1 0 FCR WR
RX
FIFO
Trigger
RX
FIFO
Trigger
0 0
DMA
Mode
Enable
TX
FIFO
Reset
RX
FIFO
Reset
FIFOs
Enable
0 1 1 LCR RD / WR Divisor
Enable
Set TX
Break
Set
Parity
Even
Parity
Parity
Enable
Stop
Bits
Word
Length
Bit-1
Word
Length
Bit-0
1 0 0 MCR RD / WR 0 0 0
Internal
Loopback
Enable
INT
Output
Enable
(OP2#)
Rsvd
(OP1#)
RTS#
Output
Control
DTR#
Output
Control
LCR[7] = 0
1 0 1 LSR RD / WR
RX
FIFO
Global
Error
THR,
TSR
Empty
THR
Empty RX Break
RX
Framing
Error
RX
Parity
Error
RX
Overrun
Error
RX
Data
Ready
1 1 0 MSR RD / WR CD#
Input
RI#
Input
DSR#
Input
CTS#
Input
Delta
CD#
Delta
RI#
Delta
DSR#
Delta
CTS#
1 1 1 SPR RD / WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
Baud Rate Generator Divisor
0 0 0 DLL RD / WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 LCR[7]=1
LCR0xBF
0 0 1 DLM RD / WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0
ST16C554 / ST16C554D / ST68C554 Data Sheet Internal Register Descriptions
9/4/19 Rev 4.0.2 15
5.0 Internal Register Descriptions
5.1 Receive Holding Register (RHR)
- Read-Only
See Receiver on page 10.
5.2 Transmit Holding Register (THR)
- Write-Only
See Transmitter on page 10.
5.3 Interrupt Enable Register (IER) -
Read and Write
The Interrupt Enable Register (IER) masks the interrupts
from receive data ready, transmit empty, line status, and
modem status registers. These interrupts are reported in
the Interrupt Status Register (ISR).
5.3.1 IER Versus Receive FIFO Interrupt
Mode Operation
When the receive FIFO (FCR bit-0 = 1) and receive
interrupts (IER bit-0 = 1) are enabled, the RHR interrupts
(see ISR bits 2 and 3) status will reflect the following:
A. The receive data available interrupts are issued to the
host when the FIFO has reached the programmed
trigger level. It will be cleared when the FIFO drops
below the programmed trigger level.
B. FIFO level will be reflected in the ISR register when the
FIFO trigger level is reached. Both the ISR register
status bit and the interrupt will be cleared when the
FIFO drops below the trigger level.
C. The receive data ready bit (LSR bit-0) is set as soon as
a character is transferred from the shift register to the
receive FIFO. It is reset when the FIFO is empty.
5.3.2 IER Versus Receive and Transmit
FIFO Polled Mode Operation
When FCR bit-0 equals a logic 1 for FIFO enable, resetting
IER bits 0 - 3 enables the FIFO polled mode of operation.
Since the receiver and transmitter have separate bits in the
LSR, either or both can be used in the polled mode by
selecting the respective transmit or receive control bit(s).
A. LSR bit-0 indicates there is data in RHR or RX FIFO.
B. LSR bit-1 indicates an overrun error has occurred and
that data in the FIFO may not be valid.
C. LSR bits 2 - 4 provide the type of receive data errors
encountered for the data byte in RHR, if any.
D. LSR bit-5 indicates THR is empty.
E. LSR bit-6 indicates both the transmit FIFO and TSR
are empty.
F. LSR bit-7 indicates a data error in at least one
character in the RX FIFO.
IER[0]: RHR Interrupt Enable
The receive data ready interrupt will be issued when RHR
has a data character in the non-FIFO mode or when the
receive FIFO has reached the programmed trigger level in
the FIFO mode.
Logic 0 = Disable the receive data ready interrupt
(default).
Logic 1 = Enable the receiver data ready interrupt.
IER[1]: THR Interrupt Enable
This bit enables the Transmit Ready Interrupt which is
issued whenever the THR becomes empty. If the THR is
empty when this bit is enabled, an interrupt will be
generated.
Logic 0 = Disable Transmit Ready interrupt (default).
Logic 1 = Enable Transmit Ready interrupt.
IER[2]: Receive Line Status Interrupt Enable
If any of the LSR register bits 1, 2, 3, or 4 is a logic 1, it will
generate an interrupt to inform the host controller about the
error status of the current data byte in FIFO. LSR bit-1
generates an interrupt immediately when an overrun
occurs. LSR bits 2 - 4 generate an interrupt when the
character in the RHR has an error.
Logic 0 = Disable the receiver line status interrupt
(default).
Logic 1 = Enable the receiver line status interrupt.
LSR (Receiver Line Status Register) RXRDY (Receive Data Time-out) RXRDY (Received Date Ready) TXRDY (Transmit Empty) MSR (Modem Status Register) None (default)
ST16C554 / ST16C554D / ST68C554 Data Sheet Interrupt Status Register (ISR)
9/4/19 Rev 4.0.2 16
IER[3]: Modem Status Interrupt Enable
Logic 0 = Disable the modem status register interrupt
(default).
Logic 1 = Enable the modem status register interrupt.
IER[7:4]: Reserved (Default 0)
5.4 Interrupt Status Register (ISR)
The UART provides multiple levels of prioritized interrupts
to minimize external software interaction. The Interrupt
Status Register (ISR) provides the user with six interrupt
status bits. Performing a read cycle on the ISR will give the
user the current highest pending interrupt level to be
serviced, others are queued up to be serviced next. No
other interrupts are acknowledged until the pending
interrupt is serviced. The Interrupt Source Table, Table 10,
shows the data values (bit 0 - 3) for the interrupt priority
levels and the interrupt sources associated with each of
these interrupt levels.
5.4.1 Interrupt Generation
LSR is by any of the LSR bits 1, 2, 3, and 4.
RXRDY is by RX trigger level.
RXRDY time-out is by a 4-character plus 12 bits delay
timer.
TXRDY is by THR empty (non-FIFO mode) or TX FIFO
empty (FIFO mode).
MSR is by any of the MSR bits 0, 1, 2, and 3.
5.4.2 Interrupt Clearing
LSR interrupt is cleared by a read to the LSR register.
RXRDY interrupt is cleared by reading data until the
FIFO falls below the trigger level.
RXRDY time-out interrupt is cleared by reading RHR.
TXRDY interrupt is cleared by a read to the ISR
register or by writing to THR.
MSR interrupt is cleared by a read to the MSR register.
ISR[0]: Interrupt Status
Logic 0 = An interrupt is pending and the ISR contents
may be used as a pointer to the appropriate interrupt
service routine.
Logic 1 = No interrupt pending (default condition).
ISR[3:1]: Interrupt Status
These bits indicate the source for a pending interrupt at
interrupt priority levels (see Interrupt Source Table 10).
ISR[5:4]: Reserved (Default 0)
ISR[7:6]: FIFO Enable Status
These bits are set to a logic 0 when the FIFOs are disabled.
They are set to a logic 1 when the FIFOs are enabled.
Table 10: Interrupt Source and Priority Level
Priority
Level
ISR Register Status Bits Source of Interrupt
Bit-3 Bit-2 Bit-1 Bit-0
1 0 1 1 0 LSR (Receiver Line Status Register)
2 1 1 0 0 RXRDY (Receive Data Time-out)
3 0 1 0 0 RXRDY (Received Data Ready)
4 0 0 1 0 TXRDY (Transmit Empty)
5 0 0 0 0 MSR (Modem Status Register)
- 0 0 0 1 None (default)
o o 1 o 1 4 1 o a 1 1 14 o o 5 (defaulk) o 1 a 1 o 7 1 1 a 0 5,615 1 (default) 1 5 1-1/2 1 6,7,8 2
ST16C554 / ST16C554D / ST68C554 Data Sheet FIFO Control Register (FCR) - Write-Only
9/4/19 Rev 4.0.2 17
5.5 FIFO Control Register (FCR) - Write-Only
This register is used to enable the FIFOs, clear the FIFOs,
set the receive FIFO trigger levels, and select the DMA
mode. The DMA and FIFO modes are defined as follows:
FCR[0]: TX and RX FIFO Enable
Logic 0 = Disable the transmit and receive FIFO
(default).
Logic 1 = Enable the transmit and receive FIFOs. This
bit must be set to logic 1 when other FCR bits are
written or they will not be programmed.
FCR[1]: RX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’.
Logic 0 = No receive FIFO reset (default).
Logic 1 = Reset the receive FIFO pointers and FIFO
level counter logic (the receive shift register is not
cleared or altered). This bit will return to a logic 0 after
resetting the FIFO.
FCR[2]: TX FIFO Reset
This bit is only active when FCR bit-0 is a ‘1’.
Logic 0 = No transmit FIFO reset (default).
Logic 1 = Reset the transmit FIFO pointers and FIFO
level counter logic (the transmit shift register is not
cleared or altered). This bit will return to a logic 0 after
resetting the FIFO.
FCR[3]: DMA Mode Select
Controls the behavior of the TXRDY# and RXRDY# pins.
See DMA operation section for details.
Logic 0 = Normal Operation (default).
Logic 1 = DMA Mode.
FCR[5:4]: Reserved (Default 0)
FCR[7:6]: Receive FIFO Trigger Select
(logic 0 = default, RX trigger level = 1)
These 2 bits are used to set the trigger level for the receive
FIFO. The UART will issue a receive interrupt when the
number of the characters in the FIFO crosses the trigger
level. Table 11 shows the complete selections.
p
5.6 Line Control Register (LCR)
- Read and Write
The Line Control Register is used to specify the
asynchronous data communication format. The word or
character length, the number of stop bits, and the parity are
selected by writing the appropriate bits in this register.
LCR[1:0]: TX and RX Word Length Select
These two bits specify the word length to be transmitted or
received.
LCR[2]: TX and RX Stop-bit Length Select
The length of stop bit is specified by this bit in conjunction
with the programmed word length.
Table 11: Receive FIFO Trigger Level Selection
FCR Bit-7 FCR Bit-6 Receive Trigger Level
0 0 1
0 1 4
1 0 8
1 1 14
Table 12: TX and RX Word Length
LCR Bit-1 LCR Bit-0 Word Length
0 0 5 (default)
0 1 6
1 0 7
1 1 8
Table 13: TX and RX Stop-Bit Length
LCR Bit-2 Word Length Stop Bit Length (Bit Time)
0 5,6,7,8 1 (default)
1 5 1-1/2
1 6,7,8 2
LCR Ell-5 LCR Ell-4 LCR Ell-G Parity Selection X X 0 No parity 0 o ’1 Odd parity 0 1 1 Even parity 1 0 '1 Force parity to mark, HIGH 1 1 1 Forced parity in space, LOW Enable or disable INT outputs to bee state. This function is associated wi see below table for details. This bit the OP2# signal during internal loo gin must be LOW during 68 mode. active or in thre NTSEL input, ed to control INTSEL
ST16C554 / ST16C554D / ST68C554 Data Sheet Modem Control Register (MCR) or General Purpose Outputs Control
9/4/19 Rev 4.0.2 18
LCR[3]: TX and RX Parity Select
Parity or no parity can be selected via this bit. The parity bit
is a simple way used in communications for a data integrity
check. See Table 14 for parity selection summary below.
Logic 0 = No parity.
Logic 1 = A parity bit is generated during the
transmission while the receiver checks for parity error
of the data character received.
LCR[4]: TX and RX Parity Select
If the parity bit is enabled with LCR bit-3 set to a logic 1,
LCR bit-4 selects the even or odd parity format.
Logic 0 = ODD Parity is generated by forcing an odd
number of logic 1’s in the transmitted character. The
receiver must be programmed to check the same
format (default).
Logic 1 = EVEN Parity is generated by forcing an even
number of logic 1’s in the transmitted character. The
receiver must be programmed to check the same
format.
LCR[5]: TX and RX Parity Select
If the parity bit is enabled, LCR bit-5 selects the forced
parity format.
LCR bit-5 = logic 0, parity is not forced (default).
LCR bit-5 = logic 1 and LCR bit-4 = logic 0, parity bit is
forced to HIGH for the transmit and receive data.
LCR bit-5 = logic 1 and LCR bit-4 = logic 1, parity bit is
forced to LOW for the transmit and receive data.
LCR[6]: Transmit Break Enable
When enabled, the Break Control Bit causes a break
condition to be transmitted (the TX output is forced to a
“space’, logic 0 state). This condition remains, until
disabled by setting LCR bit-6 to a logic 0.
Logic 0 = No TX break condition (default).
Logic 1 = Forces the transmitter output (TX) to a
“space”, logic 0, for alerting the remote receiver of a
line break condition.
LCR[7]: Baud Rate Divisors Enable
Baud rate generator divisor (DLL / DLM) enable.
Logic 0 = Data registers are selected (default).
Logic 1 = Divisor latch registers are selected.
5.7 Modem Control Register (MCR)
or General Purpose Outputs Control
- Read and Write
The MCR register is used for controlling the serial modem
interface signals or general purpose inputs and outputs.
MCR[0]: DTR# Output
The DTR# pin is a modem control output. If the modem
interface is not used, this output may be used as a general
purpose output.
Logic 0 = Force DTR# output HIGH (default).
Logic 1 = Force DTR# output LOW.
MCR[1]: RTS# Output
The RTS# pin is a modem control output. If the modem
interface is not used, this output may be used as a general
purpose output.
Logic 0 = Force RTS# output HIGH (default).
Logic 1 = Force RTS# output LOW.
MCR[2]: Reserved
OP1# is not available as an output pin on the ST16C554.
However, it is available for use during Internal Loopback
Mode. In the Loopback Mode, this bit is used to write the
state of the modem RI# interface signal.
MCR[3]: INT Output Enable
Enable or disable INT outputs to become active or in three-
state. This function is associated with the INTSEL input,
see below table for details. This bit is also used to control
the OP2# signal during internal loopback mode. INTSEL
pin must be LOW during 68 mode.
Table 14: Parity Selection
LCR Bit-5 LCR Bit-4 LCR Bit-3 Parity Selection
X X 0 No parity
0 0 1 Odd parity
0 1 1 Even parity
1 0 1 Force parity to mark, HIGH
1 1 1 Forced parity to space, LOW
0 0 Three-State 0 1 Active 1 X Active
ST16C554 / ST16C554D / ST68C554 Data Sheet Line Status Register (LSR) - Read and Write
9/4/19 Rev 4.0.2 19
Logic 0 = INT (A - D) outputs disabled (three state) in
the 16 mode (default). During internal loopback mode,
OP2# is HIGH.
Logic 1 = INT (A - D) outputs enabled (active) in the 16
mode. During internal loopback mode, OP2# is LOW.
MCR[4]: Internal Loopback Enable
Logic 0 = Disable loopback mode (default).
Logic 1 = Enable local loopback mode, see loopback
section and Table 13.
MCR[7:5]: Reserved (Default 0)
5.8 Line Status Register (LSR)
- Read and Write
This register is writeable, but it is not recommended. The
LSR provides the status of data transfers between the
UART and the host. If IER bit-2 is enabled, LSR bit-1 will
generate an interrupt immediately and LSR bits 2-4 will
generate an interrupt when a character with an error is in
the RHR.
LSR[0]: Receive Data Ready Indicator
Logic 0 = No data in receive holding register or FIFO
(default).
Logic 1 = Data has been received and can be read
from the receive holding register or RX FIFO.
LSR[1]: Receiver Overrun Flag
Logic 0 = No overrun error (default).
Logic 1 = Overrun error. A data overrun error condition
occurred in the Receive Shift Register. This happens
when additional data arrives while the FIFO is full. In
this case, the previous data in the Receive Shift
Register is overwritten. Note that under this condition
the data byte in the Receive Shift Register is not
transferred into the FIFO, therefore the data in the
FIFO is not corrupted by the error.
LSR[2]: Receive Data Parity Error Tag
Logic 0 = No parity error (default).
Logic 1 = Parity error. The receive character in RHR
does not have correct parity information and is suspect.
This error is associated with the character available for
reading in RHR.
LSR[3]: Receive Data Framing Error Tag
Logic 0 = No framing error (default).
Logic 1 = Framing error. The receive character did not
have a valid stop bit(s). This error is associated with
the character available for reading in RHR.
LSR[4]: Receive Break Tag
Logic 0 = No break condition (default).
Logic 1 = The receiver received a break signal (RX was
LOW for at least a one character frame time). In the
FIFO mode, only one break character is loaded into the
FIFO. The break indication remains until the RX input
returns to the idle condition, “mark” or HIGH.
LSR[5]: Transmit Holding Register Empty Flag
This bit is the Transmit Holding Register empty indicator.
The THR bit is set to a logic 1 when the last data byte is
transferred from the Transmit Holding Register to the
Transmit Shift Register. The bit is reset to logic 0
concurrently with the data loading to the Transmit Holding
Register by the host. In the FIFO mode, this bit is set when
the transmit FIFO is empty. It is cleared when the transmit
FIFO contains at least 1 byte.
LSR[6]: THR and TSR Empty Flag
This bit is set to a logic 1 whenever the transmitter goes
idle. It is set to logic 0 whenever either the THR or TSR
contains a data character. In the FIFO mode, this bit is set
to a logic 1 whenever the transmit FIFO and Transmit Shift
Register are both empty.
LSR[7]: Receive FIFO Data Error Flag
Logic 0 = No FIFO error (default).
Logic 1 = A global indicator for the sum of all error bits
in the RX FIFO. At least one parity error, framing error,
or break indication is in the FIFO data. This bit clears
when there is no more error(s) in any of the bytes in the
RX FIFO.
Table 15: INT Output Modes
INTSEL Pin MCR Bit-3 INT A - D Outputs in 16 Mode
0 0 Three-State
0 1 Active
1 X Active
ST16C554 / ST16C554D / ST68C554 Data Sheet Modem Status Register (MSR) - Read and Write
9/4/19 Rev 4.0.2 20
5.9 Modem Status Register (MSR) - Read and Write
This register is writeable, but it is not recommended. The
MSR provides the current state of the modem interface
input signals. The lower four bits of this register are used to
indicate the changed information. These bits are set to a
logic 1 whenever a signal from the modem changes state.
These bits may be used for general purpose inputs when
they are not used with modem signals.
MSR[0]: Delta CTS# Input Flag
Logic 0 = No change on CTS# input (default).
Logic 1 = The CTS# input has changed state since the
last time it was monitored. A modem status interrupt
will be generated if the MSR interrupt is enabled (IER
bit-3).
MSR[1]: Delta DSR# Input Flag
Logic 0 = No change on DSR# input (default).
Logic 1 = The DSR# input has changed state since the
last time it was monitored. A modem status interrupt
will be generated if the MSR interrupt is enabled (IER
bit-3).
MSR[2]: Delta RI# Input Flag
Logic 0 = No change on RI# input (default).
Logic 1 = The RI# input has changed from LOW to
HIGH, ending of the ringing signal. A modem status
interrupt will be generated if the MSR interrupt is
enabled (IER bit-3).
MSR[3]: Delta CD# Input Flag
Logic 0 = No change on CD# input (default).
Logic 1 = Indicates that the CD# input has changed
state since the last time it was monitored. A modem
status interrupt will be generated if the MSR interrupt is
enabled (IER bit-3).
MSR[4]: CTS Input Status
A HIGH on the CTS# pin will stop the UART transmitter as
soon as the current character has finished transmission. A
LOW will resume data transmission. Normally the MSR bit-
4 is the compliment of the CTS# input. However in the
loopback mode, this bit is equivalent to the RTS# bit in the
MCR register. The CTS# input may be used as a general
purpose input when the modem interface is not used.
MSR[5]: DSR Input Status
Normally this bit is the complement of the DSR# input. In
the loopback mode, this bit is equivalent to the DTR# bit in
the MCR register. The DSR# input may be used as a
general purpose input when the modem interface is not
used.
MSR[6]: RI Input Status
Normally this bit is the complement of the RI# input. In the
loopback mode, this bit is equivalent to bit-2 in the MCR
register. The RI# input may be used as a general purpose
input when the modem interface is not used.
MSR[7]: CD Input Status
Normally this bit is the complement of the CD# input. In the
loopback mode, this bit is equivalent to bit-3 in the MCR
register. The CD# input may be used as a general purpose
input when the modem interface is not used.
5.10 Scratch Pad Register (SPR)
- Read and Write
This is a 8-bit general purpose register for the user to store
temporary data.
Registers DLM and DLL are unknown upon power up. They RHR Bits 7 - U = OXXX THR Bits 7 - U = OXXX IER Bits 7 - U = 0x00 FCR Bits 7 - U = 0x00 ISR Bits 7 - U = 0x01 LCR Bits 7 - U — 0x00 MCR Bits 7 - — 0x00 LSR Bits 7 - 0 = 0x60 Bits 3 - 0 = Logic 0 SPR Bits 7 - U = OXFF IIO Signals TX HIGH IRTX LOW RTSI? HIGH DTR# HIGH RXRDW? HIGH TXRDY# LOW INT |RQ#
ST16C554 / ST16C554D / ST68C554 Data Sheet Baud Rate Generator Registers (DLL and DLM) - Read and Write
9/4/19 Rev 4.0.2 21
5.11 Baud Rate Generator Registers (DLL and DLM) - Read and Write
These registers make-up the value of the baud rate divisor.
The concatenation of the contents of DLM and DLL gives
the 16-bit divisor value. See Programmable Baud Rate
Generator on page 9.
Table 16: UART Reset Conditions for Channels A - D
Item Reset State
Registers
DLM, DLL DLM and DLL are unknown upon power up. They
do not reset when the Reset Pin is asserted.
RHR Bits 7 - 0 = 0xXX
THR Bits 7 - 0 = 0xXX
IER Bits 7 - 0 = 0x00
FCR Bits 7 - 0 = 0x00
ISR Bits 7 - 0 = 0x01
LCR Bits 7 - 0 = 0x00
MCR Bits 7 - 0 = 0x00
LSR Bits 7 - 0 = 0x60
MSR Bits 3 - 0 = Logic 0
Bits 7 - 4 = Logic levels of the inputs inverted
SPR Bits 7 - 0 = 0xFF
I/O Signals
TX HIGH
IRTX LOW
RTS# HIGH
DTR# HIGH
RXRDY# HIGH
TXRDY# LOW
INT
(16 Mode) LOW
IRQ#
(68 Mode) HIGH (INTSEL = LOW)
Power supply range 7.0 V V c + 0.3v Operafing kemperature See Ordering Information. Smrage temperamre —65 150 “C Package Dissipakion 500 mW LQFP64 50 11 “C/W PL0068 46 17 “C/W v v v v v v v v |L=5mA |L=4mA lH—-5mA lH—-1mA
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Specifications
9/4/19 Rev 4.0.2 22
6.0 Specifications
6.1 Absolute Maximum Ratings
1. Margin of error: ±15%
6.2 Electrical Characteristics
6.2.1 DC Electrical Characteristics
Unless otherwise noted: TA = 0°C - 70°C (–40°C to +85°C for industrial grade package), VCC = 2.97V to 5.5V .
Table 17: Absolute Maximum Ratings
Parameter Minimum Maximum Units
Power supply range 7.0 V
Voltage at any pin GND – 0.3 VCC + 0.3V V
Operating temperature See Ordering Information.
Storage temperature 65 150 °C
Package Dissipation 500 mW
Table 18: Typical Package Thermal Resistance Data(1)
Package ѲJA ѲJC Units
LQFP64 50 11 °C/W
PLCC68 46 17 °C/W
Table 19: Electrical Characteristics
Symbol Parameter Conditions Limits (3.3V) Limits (5.0V) Units
Minimum Maximum Minimum Maximum
VILCK Clock input low level -0.3 0.6 -0.3 0.6 V
VIHCK Clock input high level 2.4 VCC 3.0 VCC V
VIL Input low voltage -0.3 0.8 -0.3 0.8 V
VIH Input high voltage 2.0 VCC 2.2 VCC V
VOL Output low voltage
IOL = 5mA 0.4 V
IOL = 4mA 0.4 V
VOH Output high voltage
IOH = -5mA 2.4 V
IOH = -1mA 2.0 V
IIL Input low leakage current ±10 ±10 µA
IIH Input high leakage current ±10 ±10 µA
CIN Input pin capacitance 5 5 pF
ICC Power supply current 3 6 mA
CLK Extemal clock low / high time ns OSC UART crystal or external clock frequency MHz -|-l-l-l-l-l-l-l-l-l-l-l-l-lHH-l-l-l-l-l-l-l-l-l-l-l-l-l-l-l-l
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Electrical Characteristics
9/4/19 Rev 4.0.2 23
6.2.2 AC Electrical Characteristics
TA = 0°C - 70°C (–40°C to +85°C for industrial grade package), VCC = 2.97V to 5.5V, 70pF load where applicable.
Table 20: AC Electrical Characteristics
Symbol Parameter
Limits
3.3V ±10%
Limits
5.0V ±10% Units
Minimum Maximum Minimum Maximum
CLK External clock low / high time 63 21 ns
OSC UART crystal or external clock frequency 8 24 MHz
TAS Address setup time (16 Mode) 5 0 ns
TAH Address hold time (16 Mode) 5 5 ns
TCS Chip select width (16 Mode) 80 50 ns
TRD IOR# strobe width (16 Mode) 80 50 ns
TDY Read cycle delay (16 Mode) 40 30 ns
TRDV Data access time (16 Mode) 40 25 ns
TDD Data disable time (16 Mode) 25 15 ns
TWR IOW# strobe width (16 Mode) 35 25 ns
TDY Write cycle delay (16 Mode) 40 30 ns
TDS Data setup time (16 Mode) 20 15 ns
TDH Data hold time (16 Mode) 5 5 ns
TADS Address setup (68 Mode) 10 10 ns
TADH Address hold (68 Mode) 15 15 ns
TRWS R/W# setup to CS# (68 Mode) 10 10 ns
TRDA Data access time (68 mode) 40 25 ns
TRDH Data disable time (68 mode) 25 15 ns
TWDS Write data setup (68 mode) 20 15 ns
TWDH Write data hold (68 Mode) 10 10 ns
TRWH CS# de-asserted to R/W# de-asserted (68 Mode) 10 10 ns
TCSL CS# strobe width (68 Mode) 80 50 ns
TCSD CS# cycle delay (68 Mode) 40 30 ns
TWDO Delay from IOW# to output 50 40 ns
TMOD Delay to set interrupt from MODEM input 40 35 ns
TRSI Delay to reset interrupt from IOR# 40 35 ns
TSSI Delay from stop to set interrupt 1 1 Bclk
TRRI Delay from IOR# to reset interrupt 45 40 ns
TSI Delay from start to interrupt 45 40 ns
TINT Delay from initial INT reset to transmit start 8 24 8 24 Bclk
TWRI Delay from IOW# to reset interrupt 45 40 ns
TSSR Delay from stop to set RXRDY# 1 1 Bclk
TRR Delay from IOR# to reset RXRDY# 45 40 ns
TWT Delay from IOW# to set TXRDY# 45 40 ns
Bclk Baud clock 16X of dala rate Hz
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Electrical Characteristics
9/4/19 Rev 4.0.2 24
Figure 14: Clock Timing
Figure 15: Modem Input and Output Timing for Channels A - D
TSRT Delay from center of start to reset TXRDY# 8 8 Bclk
TRST Reset pulse width 40 40 ns
N Baud rate divisor 1 216-1 1216-1 -
Bclk Baud clock 16X of data rate Hz
Table 20: AC Electrical Characteristics
Symbol Parameter
Limits
3.3V ±10%
Limits
5.0V ±10% Units
Minimum Maximum Minimum Maximum
OSC
CLK
CLK
EXTERNAL
CLOCK
IO W #
IO W
RTS#
DTR#
CD#
CTS#
DSR#
IN T
IO R #
RI#
TWDO
TMOD TMOD
TRSI
TMOD
Active
Active
Change of state Change of state
A c tive A c tive Active
Change of state Change of state
Change of state
Active Active
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Electrical Characteristics
9/4/19 Rev 4.0.2 25
Figure 16: 16 Mode (Intel) Data Bus Read Timing for Channels A - D
Figure 17: 16 Mode (Intel) Data Bus Write Timing for Channels A - D
TAS
TDD
TAH
TRD
TRDV
TDY
TDD
TRDV
TAH
TAS
TCS
Valid Address Valid Address
Valid Data Valid Data
A0-A7
CS#
IOR#
D0-D7
RDTm
TCS
TRD
16Write
TAS
TDH
TAH
TWR
TDS
TDY
TDH
TDS
TAH
TAS
TCS
Valid Address Valid Address
Valid Data Valid Data
A0-A7
CS#
IOW#
D0-D7
TCS
TWR
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Electrical Characteristics
9/4/19 Rev 4.0.2 26
Figure 18: 68 Mode (Motorola) Data Bus Read Timing for Channels A - D
Figure 19: 68 Mode (Motorola) Data Bus Write Timing for Channels A - D
68Read
TADS
TRDH
TADHTCSL
TRDA
TCSD
TRWS
Valid Address Valid Address
Valid Data
A0-A7
CS#
R/W#
D0-D7
TRWH
Valid Data
68Write
TADS
TADHTCSL
TWDS
TCSD
TRWS
Valid Address Valid Address
Valid Data
A0-A7
CS#
R/W#
D0-D7
TRWH
Valid Data
TWDH
r); 457 —1’:
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Electrical Characteristics
9/4/19 Rev 4.0.2 27
Figure 20: Receive Ready and Interrupt Timing (Non-FIFO Mode) for Channels A - D
Figure 21: Transmit Ready and Interrupt Timing (Non-FIFO Mode) for Channels A - D
RX
RXRDY#
IOR#
INT
D0:D7
Start
Bit D0:D7
Stop
Bit D0:D7
TSSR
1 Byte
in RHR
Active
Data
Ready
Active
Data
Ready
Active
Data
Ready
1 Byte
in RHR
1 Byte
in RHR
TSSR TSSR
RXNFM
TRR TRR TRR
TSSR TSSR TSSR
(Reading data
out of RHR)
TX
TXRDY#
IOW#
INT*
D0:D7
Start
Bit D0:D7
Stop
Bit D0:D7
TWT
TXNonFIFO
TWT TWT
TWRI TWRI TWRI
TSRT TSRT TSRT
*INT is cleared when the ISR is read or when data is loaded into the THR.
ISR is read ISR is readISR is read
(Loading data
into THR)
(Unloading)
IER[1]
enabled
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Electrical Characteristics
9/4/19 Rev 4.0.2 28
Figure 22: Receive Ready and Interrupt Timing (FIFO Mode, DMA Disabled) for Channels A - D
Figure 23: Receive Ready and Interrupt Timing (FIFO Mode, DMA Enabled) for Channels A - D
RX
RXRDY#
IOR#
INT
D0:D7
S
TSSR
RXINTDMA#
RX FIFO fills up to RX
Trigger Level or RX Data
Timeout
RX FIFO drops
below RX
Trigger Level
FIFO
Empties
First Byte is
Received in
RX FIFO
D0:D7
SD0:D7TD0:D7
SD0:D7
S
TD0:D7
S
TTD0:D7
ST
Start
Bit
Stop
Bit
TRR
TRRI
TSSI
(Reading data out
of RX FIFO)
RX
RXRDY#
IOR#
INT
D0:D7
S
TSSR
RXFIFODMA
RX FIFO fills up to RX
Trigger Level or RX Data
Timeout
RX FIFO drops
below RX
Trigger Level
FIFO
Empties
D0:D7
SD0:D7TD0:D7
SD0:D7
S
TD0:D7
S
TTD0:D7
ST
Start
Bit
Stop
Bit
TRR
TRRI
TSSI
(Reading data out
of RX FIFO)
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Electrical Characteristics
9/4/19 Rev 4.0.2 29
Figure 24: Transmit Ready and Interrupt Timing (FIFO Mode, DMA Disabled) for Channels A - D
Figure 25: Transmit Ready and Interrupt Timing (FIFO Mode, DMA Enabled) for Channels A - D
TX
TXRDY#
IOW#
INT*
D0:D7
SD0:D7TD0:D7
SD0:D7
S
TD0:D7
S
TTD0:D7
ST
Start
Bit
Stop
Bit
(Unloading)
(Loading data
into FIFO)
Last Data Byte
Transmitted
Data in
TX FIFO
TX FIFO
Empty
TWT
TSI
TX FIFO
Empty
T
TS
ISR is read
IER[1]
enabled
ISR is read
*INT is cleared when the ISR is read or when at least 1 byte is written to the TX FIFO.
TWRI
TX
TXRDY#
IOW#
INT*
D0:D7
SD0:D7
TD0:D7
SD0:D7
S
TD0:D7
S
TTD0:D7
ST
Start
Bit
Stop
Bit
(Unloading)
(Loading data
into FIFO)
Last Data Byte
Transmitted
TSI
TX FIFO
Empty
T
TS
ISR is read
IER[1]
enabled
ISR is read
*INT is cleared when the ISR is read or when at least 1 byte is written to the TX FIFO.
TWRI
At least 1
empty location
in FIFO
TSRT
TX FIFO
Full
TWT
HHHHHHHW‘HHHHHHHH MIIJMPM 15m ’U‘ “L r \ a g\ 4 , w..." ‘J l " man u. “ DITAIL A sawswzj L ! 1 mm -|'l— 4-5-— slnivliw mmsum u w nwam m mm m m mu. m um, m w. A Ian mm Al am ms we: won .2 us m m Ms; mass m b an m an mm mm m E; E; : am am new was # E . «Jaw: am w: r—‘ :u a mu am: an w: \:l |:| m mum moms: # E g qu ms: um m: .H |:' + E: a I an ms: mu m: g1 L 45 m 015 mm me «use l—\ |:| n mu .2: mm m. |:l : m run 0.1m # E n m can am: can :u :1 s a .15 7 n u 7 1—1 E a: o a 7 a2 n u u u w u a; n ‘1 u u ‘2 u <1 m="" us-m="" aw]="" .="" mus="" ,="" la="" ,="" a:="" u="" terminal="" mension="" typical="">
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Mechanical Dimensions
9/4/19 Rev 4.0.2 30
7.0 Mechanical Dimensions
7.1 LQFP64
Figure 26: Mechanical Dimension, LQFP64 (10 x 10 x 1.4mm Low-Profile Quad Flat Pack)
1. Control dimensions are in Millimeters
2. Dimensions and tolerance per Jedec MS-026
Drawing No. : POD - 00000092
Revision: A
SIDE VIEW
TOP VIEW
TYPICAL RECOMMENDED LAND PATTERN
TERMINAL DIMENSION
DETAIL A
/ w Mm NOM MAX swam A 4.19 4.37 4.57 A1 2.29 2.67 3.05 a — A. A3 0.51 7 7 1k u 25m 25.45 25.27 m 24.43 2423 2433 D3 2 .32 REF E 2502 2535 25.27 E‘ 24.13 2423 24.33 E3 2u.32 REF H L07 \ 7 \ 4 42 2 ‘27 BSC R 0.54 — LN _ w 0 as u 74 0.51 w W a 33 0.43 o 53 N 95 , ALL DIMENSIDNS ARE IN MILLIMETERS, ANGLES ARE IN DEGREES 7 DIMENSIDN: AND TEILERANCE PER JEDEC Msiuma. 2 non
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet PLCC68
9/4/19 Rev 4.0.2 31
7.2 PLCC68
Figure 27: Mechanical Dimensions, PLCC68 (Plastic Leaded Chip Carrier)
R
e
vi
s
i
o
n
:
A
Drawing No.: POD-000000
TOP VIEW
TERMINAL DETAILS
SIDE VIEW
SIDE VIEW
44
60
68
1
9
10
26
43
27
61
D1
E
D
E1
Pin 1 I.D. Mark
E3
D3
SEATING
PLANE
A
A1
R
A3
45º x H
145
ST16C554 ST1605540064-F 0°C to 70°C ‘ LQFP64 ‘ Tray ‘ Yes ST160554D ST160554DCQS4-F 0°C :0 70°C LQFP64 Tray Yes ST160554D|064-F —40°C to +as°c LQFP64 Tray Yes ST160554D|064TR-F —40°C to +as°c LQFP64 Reel Yes ST160554DCJ68-F 0°C :0 70°C PLCCGS Tube Yes ST160554DCJ68TR—F 0°C :0 70°C PLCCGS Reel Yes sneesmouea—F —40°C m +85“C PLCCGS Tube Yes ST160554DIJ68TR-F —40°C m +85“C PLCCGS Reel Yes ST680554 STGSCSMIJGa-F —40°C to +85“C PLCCSS Tube Yes
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Ordering Information
9/4/19 Rev 4.0.2 32
8.0 Ordering Information
1. Refer to www.maxlinear.com/ST16C554, www.maxlinear.com/ST16C554D, and www.maxlinear.com/ST68C554 for most up-to-date Ordering
Information.
2. Visit www.maxlinear.com for additional information on Environmental Rating.
Table 21: Ordering Information(1)
Ordering Part Number Operating Temperature Range Package Packaging Method Lead-Free(2)
ST16C554
ST16C554CQ64-F 0°C to 70°C LQFP64 Tray Yes
ST16C554D
ST16C554DCQ64-F 0°C to 70°C LQFP64 Tray Yes
ST16C554DIQ64-F 40°C to +85°C LQFP64 Tray Yes
ST16C554DIQ64TR-F 40°C to +85°C LQFP64 Reel Yes
ST16C554DCJ68-F 0°C to 70°C PLCC68 Tube Yes
ST16C554DCJ68TR-F 0°C to 70°C PLCC68 Reel Yes
ST16C554DIJ68-F 40°C to +85°C PLCC68 Tube Yes
ST16C554DIJ68TR-F 40°C to +85°C PLCC68 Reel Yes
ST68C554
ST68C554IJ68-F 40°C to +85°C PLCC68 Tube Yes
/\ MAXLINEAR V
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Maxlinear, Inc. does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be
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product names appearing herein are the property of their respective owners.
© 2004 - 2019 MaxLinear, Inc. All rights reserved.
ST16C554 / ST16C554D / ST68C554 2.97V to 5.5V Quad UART with 16-Byte FIFO Data Sheet Disclaimer
MaxLinear, Inc.
5966 La Place Court, Suite 100
Carlsbad, CA 92008
760.692.0711 p.
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www.maxlinear.com

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