RS232 Quick Guide Datasheet by Analog Devices Inc.

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L, LT, LTC, LTM, Linear Technology and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
RS232 Quick Guide
TIA/EIA-232-F Standard
RS232 conveys data over a simple unterminated, multiconductor cable at rates up to 20kB. The RS232 standard specifies the electrical characteristics
and connector for an all encompassing point-to-point modem interface. Although the original specification was intended for modems, subsequent
renderings shed unneeded signals to expand its scope and use as a general purpose serial interface at data rates up to 1MB.
Signal Pinout
DB25 DB9 Name ABBR. DTE DCE
1 Frame Ground FG
2 3 Transmit Data TD
3 2 Receive Data RD
4 7 Request to Send RTS
5 8 Clear to Send CTS
6 6 Data Set Ready DSR
7 5 Signal Ground SG
8 1 Data Carrier Detect DCD
9 (Reserved)
10 (Reserved)
11 Unassigned
12 Sec. Carrier Detect (S) CD
13 Sec. Clear to Send (S) CTS
14 Sec. Transmit Data (S) TD
15 Transmitter Clock TC
16 Sec. Receive Data (S) RD
17 Receiver Clock RC
18 Local Loopback
19 Sec. Request to Send (S) RTS
20 4 Data Terminal Ready DTR
21 Remote Loopback
Signal Quality Detect SQ
22 9 Ring Indicator RI
23 Data Rate Select
24 Transmitter Clock (E) TC
25 Test Mode
n The DTE DCE column indicates data direction.
n Pin numbers in bold indicate commonly used signals.
n Data rate select (Pin 23) can be from DTE or DCE.
Connectors
Specification RS232
Mode of Operation Single-Ended
Number of Drivers and Receivers Allowed on One Line 1 Driver, 1 Receiver
Maximum Cable Length 50 Feet*
Maximum Data Rate 20kB/s
Maximum Voltage Applied to Driver Output ±25V
Driver Output Signal Minimum Loaded ±5V
Maximum Unloaded ±15V
Termination 3k to 7k
Output Slew Rate 30V/µs (Max)
Receiver Input Voltage Range ±25V Max
Receiver Input Sensitivity ±3V
Receiver Input Resistance 3k to 7k
* For 2500pF cable capacitance, as per IEA 232D for data rates less than 20k baud. For data rates greater than 20k baud, CLOAD = 1000pF.
Character FrameRelative Signal Timing
Cable and Adapters
DTE
1
2
3
4
5
6
7
8
15
17
20
DCE
2
3
7
4
5
6
8
20
DTE
2
3
7
4
5
6
8
20
DCE
1
2
3
4
5
6
7
8
15
17
20
FG
Straight Through
Cable
Minimum Straight
Cable
TD
RD
RTS
CTS
DSR
SG
TD
RD
SG
RTS
CTS
DSR
DCD
DTR
RTS
CTS
DSR
DCD
DTR
DCD
TC (SYNC. ONLY)
RC (SYNC. ONLY)
DTR
DTE
1
7
2
3
4
5
6
8
20
DCE
1
7
2
3
4
5
20
6
8
FG
Null Modem Cable
SG
TD
RD
RTS
CTS
DSR
DCD
DTR
TD
RD
RTS
CTS
DTR
DSR
DCD
25-PIN
2
3
4
5
6
7
8
20
22
9-PIN
3
2
7
8
6
5
1
4
9
TD
AT to 25-Pin Adapter
RD
RTS
CTS
DSR
SG
DCD
DTR
RI
A minimum null modem cable is the same as a minimum straight cable except that RD and
TD (Pins 2 and 3) are cross-connected as in the null modem cable.
25 24 23 22 21 20 19 18 17 16 15 14
13 12 11 10 9 8 7 6 5 4 3 2 1
9 8 7 6
5 4 3 2 1
DB25 DB9 Views are from the pin
side of the female
(DCE) connector or
the wire side of the
male (DTE) connector.
DTR
DSR
RTS
CTS
TD
Normal timing sequences during establishment of
communications are shown below. On half-duplex
circuits, RTS is dropped as soon as the data is sent.
This is to signal a turnaround of the circuit. START
BIT
STOP
BIT
LSB
OTHER DATA BITS
MSB = MOST SIGNIFICANT DATA BIT
LSB = LEAST SIGNIFICANT DATA BIT
OPTIONAL PARITY BIT
• • • MSB
DATA BIT
CHARACTER FRAME
PAR
Numbsrof Numbsvof Supply DaIaRals ESD Driver Shumown Temp. PanNumbev Drivers Rsceivsvs (V) (kbps) (kV) Disable Mods Grads Packages LTMzsszra/rs 3 3/5 moo 10 C \ LGArsz. EGA732 LTCzsm 1 8 m 5 250 10 C \ DFNVIZ LTHssA C \ SW24. N724 Periphavsl (DCE) LmssA 5 3 5 250 m <3 mm="" n-20="" homes="" 2="" 2="" 3="" 3="" ‘20="" m="" c“="" 50-16="" www.linenr.cnmlfi$232="" technology="">
www.linear.com/RS232 n 1-800-4-LINEAR
1010B
Linear Technology RS232 Transceivers
Part Number
Number of
Drivers
Number of
Receivers
Supply
(V)
Data Rate
(kbps)
ESD
(kV)
Driver
Disable
Shutdown
Mode
Temp.
Grade Packages
LTM2882-3/-5 1 1 3.3/5 1000 10 C, I LGA-32, BGA-32
LTC2801 1 1 1.8 to 5 250 10 C, I DFN-12
LTC2802 1 1 1.8 to 5 1000 10 C, I DFN-12
LT1180A 2 2 5 250 10 C, I SW-18, N-18
LT1181A 2 2 5 250 10 C, I SW-16, N-16
LT1280A 2 2 5 250 10 C, I SW-16, N-18
LT1281A 2 2 5 250 10 C, I SW-16, N-16
LT1381 2 2 5 250 10 C, I SO-16
LT1780 2 2 5 250 15 C, I SW-18, N-18
LT1781 2 2 5 250 15 C, I SO-16, SW-16, N-16
LTC1080 2 2 5 120 2 C, I SW-18, N-18
LTC1081 2 2 5 120 2 C, I SO-16, N-16
LTC1382 2 2 5 120 10 C, I SW-18, N-18
LTC1383 2 2 5 120 10 C, I SO-16, N-16
LTC1384 2 2 5 120 10 C, I SSOP-20, DIP-18, SO-18
LTC2803 2 2 1.8 to 5 250 10 C, I DFN-16
LTC2803-1 2 2 1.8 to 5 250 10 C, I SSOP-16
LTC2804 2 2 1.8 to 5 1000 10 C, I DFN-16
LTC2804-1 2 2 1.8 to 5 1000 10 C, I SSOP-16
LT1039A 3 3 5 250 15 C, I SW-16, N-16
LT1032 4 0 5 250 2 C, I SW-14, N-14
LT1134A 4 4 5 250 10 C, I SW-24, N-24
LT1136A 4 5 5 250 10 C SW-28, N-28
LT1139A 4 4 5 250 10 C SW-24, N-24
LT1130A 5 5 5 250 10 C, I SW-28, N-28
LT1131A 5 4 5 250 10 C SW-28, N-28
LT1133A 3 5 5 250 15 C, I SW-24, N-24
LT1137A 3 5 5 250 15 C, I SSOP-28, SW-28, N-28
LT1141A 3 5 5 250 10 C SW-24, N-24
LT1237 3 5 5 250 15 C SSOP-28, SW-28, N-28
LT1330 3 5 5 250 10 C, I SSOP-28, SW-28, N-28
LT1342 3 5 5 250 10 C SSOP-28, SW-28, N-28
LT1537 3 5 5 250 2 C SSOP-28, SW-28
LTC1337 3 5 5 120 10 C SSOP-28, SW-28, N-28
LTC1347 3 5 5 120 10 C SSOP-28, SW-28, N-28
LTC1348 3 5 3 to 5.5 120 10 C, I SSOP-28, SW-28
LTC1349 3 5 5 120 10 C, I SSOP-28, SW-28, N-28
LT1132A 5 3 5 250 10 C, I SW-24, N-24
LT1135A 5 3 5 250 10 C SW-20, N-20
LT1138A 5 3 5 250 10 C, I SSOP-28, SW-28, N-28
LT1140A 5 3 5 250 10 C SW-24, N-24
LTC1338 5 3 5 120 10 C, I SSOP-28, SW-28, N-28
LTC1385 2 2 3.3 120 10 C, I SSOP-20, SO-18, DIP-18
LTC1386 2 2 3.3 120 10 C, I SO-16
LT1331 3 5 3 to 5 250 10 C SSOP-28, SW-28, N-28
LTC1327 3 5 3.3 120 10 C SSOP-28, SW-28, N-28
LTC1350 3 5 3.3 250 10 C, I SSOP-28, SW-28, N-28
2500VRMS Isolation
PC Port (DTE)
Peripheral (DCE)
General Purpose
RS562

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