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Interface
Standards
There
are a variety of data communications standards which can leave you totally
confused. Fear not, they are actually fairly simple and easy to understand.
Each
standard defines the pinout (pin number and designation), connector
type, voltage levels on each pin, and the maximum data rate and maximum
distance of cable run.
The
following Pinout tables are correct to the best of our knowledge and
are reviewed regularly.
EIA-232
(CCITT V.24) / RS-232 ( 25 Way D-Type & PC Comm Port 9 Way D-Type
)
This
specifies a 25 pin D Type connector as a standard unbalanced (single
wire signals) interface for DCE (Data Communication Equipment - Modem)
or DTE (Data Termination Equipment - PC Comm Port or User Equipment).
EIA-422
(CCITT V.11) / RS-422
This
specifies a 37 pin D Type connector as a standard balanced (signal pairs)
synchronous (data and clocks) interface for DCE (Data Communication
Equipment - Modem) or DTE (Data Termination Equipment - User Equipment).
This interface can also be on 9 way D Types and 15 way D Types.
V.35
/ EIA-449 / RS-449
This
specifies a 37 pin D Type connector as a standard balanced (signal pairs)
synchronous (data and clocks) interface for DCE (Data Communication
Equipment - Modem) or DTE (Data Termination Equipment - User Equipment).
EIA-530
(CCITT ) / RS-530
This
specifies a 25 pin D Type connector as a standard balanced (signal pairs)
synchronous (data and clocks) interface for DCE (Data Communication
Equipment - Modem) or DTE (Data Termination Equipment - User Equipment).
This interface is identical to RS-422 but uses a 25 Way connector and
is also used for RS-423 which is the same interface again but unbalanced.
X-21
This
specifies a 15 pin D Type connector as a standard balanced (signal pairs)
synchronous (data and clocks) interface for DCE (Data Communication
Equipment - Modem) or DTE (Data Termination Equipment - User Equipment).
This interface has only one clock.
EIA-423
/ RS-423
This
specifies a 25 pin D Type connector as a standard unbalanced synchronous
(data and clocks) interface for DCE (Data Communication Equipment -
Modem) or DTE (Data Termination Equipment - User Equipment). This interface
is almost identical to RS-422 but for RS-423 is unbalanced. Very similar
to RS-232 but can drive longer cable lengths at higher data rates.
Pinout
Tables
| EIA-232
/ RS - 232 (
Various Connector Types - Mainly 25 Way D Type ) |
| |
|
|
|
|
|
| Pin |
Description |
Connector
Type |
DTE |
DCE |
Notes |
| 2 |
Tx
Data |
25
Way D-Type |
Data
Out |
Data
In |
|
| 3 |
Rx
Data |
|
Data
In |
Data
Out |
|
| 7 |
Signal
ground |
|
|
|
|
| 15 |
Tx
Clock |
|
Clock
Out |
Clock
In |
|
| 17 |
Rx
Clock |
|
Clock
Out |
Clock
In |
|
| 24 |
Tx
Clock |
|
Clock
In |
Clock
Out |
|
| |
|
|
|
|
|
| EIA-232
/ RS - 232 ( PC Comm Port - 9 Way D Type ) |
| |
|
|
|
|
|
| Pin |
Description |
Connector
Type |
DTE(PC)
|
DCE |
Notes |
| |
|
|
|
|
|
| 1 |
DCD
Data Carrier Detect |
9
Way D-Type Male |
Data
In |
Data
Out |
|
| 2 |
Rx
Data |
|
Data
In |
Data
Out |
|
| 3 |
Tx
Data |
|
Data
Out |
Data
In |
|
| 4 |
DTR
Data Terminal Ready |
|
Data
Out |
Data
In |
|
| 5 |
Signal
Ground |
|
|
|
|
| 6 |
DSR
Data Set Ready |
|
Data
In |
Data
Out |
|
| 7 |
RTS
Request to Send |
|
Data
Out |
Data
In |
|
| 8 |
CTS
Clear to Send |
|
Data
In |
Data
Out |
|
| 9 |
RI
Ring Indicator |
|
Data
In |
Data
Out |
|
| |
|
|
|
|
|
|
|
|
|
|
|
| EIA-422
/ RS - 422 ( Various Connector Types - Mainly 37 Way D Type ) |
| |
|
|
|
|
|
| Pin |
Description |
Designation
/ Label |
DCE |
DTE |
Notes |
|
|
|
|
|
|
| 1 |
Shield |
|
|
|
|
| 2 |
Signal
Rate Indicator |
S |
In |
Out |
|
| 3 |
N/C |
|
|
|
|
| 4 |
Send Data (A)
|
SD-
|
Data
In |
Data
Out |
|
| 5 |
Send
Timing (A)
|
ST-
|
Clock
Out |
Clock
In |
|
| 6 |
Receive
Data (A)
|
RD-
|
Data
Out |
Data
In |
|
| 7 |
Request
To Send (A)
|
RS-
|
In |
Out
|
|
| 8 |
Receive
Timing (A)
|
RT- |
Clock
Out |
Clock
In |
|
| 9 |
Clear
To Send (A)
|
CS- |
Out |
In |
|
| 10 |
Local
Loopback
|
LL |
In |
Out |
|
| 11 |
Data
Mode (A)
|
DM-
|
Out |
In |
|
| 12 |
Terminal
Ready (A)
|
TR-
|
In |
Out |
|
| 13 |
Receiver
Ready (A)
|
RR- |
Out |
In |
|
| 14 |
Remote
Loopback
|
RL |
In |
Out |
|
| 15 |
Incoming
Call
|
IC
|
Out |
In |
|
| 16 |
Signal
Freq./Sig. Rate Select.
|
SF/SR+ |
Out/In |
In/Out
|
|
| 17 |
Terminal
Timing (A)
|
TT-
|
Clock
In |
Clock
Out |
|
| 18 |
Test
Mode (A)
|
TM- |
Out |
In |
|
| 19 |
Signal
Ground
|
SG |
|
|
|
| 20 |
Receive
Common
|
RC |
|
|
|
| 21 |
N/C |
|
|
|
|
| 22 |
Send
Data (B)
|
SD+ |
Data
In |
Data
Out |
|
| 23 |
Send
Timing (B)
|
ST+
|
Clock
Out |
Clock
In |
|
| 24 |
Receive
Data (B)
|
RD+
|
Data
Out |
Data
In |
|
| 25 |
Request
To Send (B)
|
RS+
|
In |
Out |
|
| 26 |
Receive
Timing (B)
|
RT+ |
Clock
Out |
Clock
In |
|
| 27 |
Clear
To Send (B)
|
CS+ |
Out |
In |
|
| 28 |
Terminal
In Service
|
IS
|
In |
Out |
|
| 29 |
Data
Mode (B)
|
DM+
|
Out |
In |
|
| 30 |
Terminal
Ready (B)
|
TR+
|
In |
Out |
|
| 31 |
Receiver
Ready (B)
|
RR+
|
Out |
In |
|
| 32 |
Select
Standby
|
SS |
Out |
In |
|
| 33 |
Signal
Quality
|
SQ |
Out |
In |
|
| 34 |
New
Signal
|
NS |
In |
Out |
|
| 35 |
Terminal
Timing (B)
|
TT+
|
Clock
In |
Clock
Out |
|
| 36 |
Standby
Indicator
|
SB |
Out |
In |
|
| 37 |
Send
Common
|
SC |
|
|
|
|
|
|
|
|
|
| EIA-423
/ RS - 423 |
| |
|
|
|
|
|
| Pin |
Description |
Connector
Type |
DTE |
DCE |
Notes |
| |
|
|
|
|
|
| 2 |
Tx
Data |
25
Way D-Type |
Data
Out |
Data
In |
|
| 3 |
Rx
Data |
|
Data
In |
Data
Out |
|
| 7 |
Signal
ground |
(Can
be a variety of Connectors) |
|
|
|
| 15 |
Tx
Clock |
|
Clock
Out |
Clock
In |
|
| 17 |
Rx
Clock |
|
Clock
Out |
Clock
In |
|
| 24 |
Tx
Clock |
|
Clock
In |
Clock
Out |
|
| |
|
|
|
|
|
|
|
|
|
|
|
| X-21 |
| |
|
|
|
|
|
| Pin |
Description |
Connector
Type |
DCE |
DTE |
Notes |
| 2 |
Tx
Data A |
15
Way D-Type |
Data
In |
Data
Out |
|
| 9 |
Tx
Data B |
|
Data
In |
Data
Out |
|
| 4 |
Rx
Data A |
|
Data
Out |
Data
In |
|
| 11 |
Rx
Data B |
|
Data
Out |
Data
In |
|
| 8 |
Signal
ground |
|
|
|
|
| 6 |
Tx
Clock A |
|
Clock
Out |
Clock
In |
|
| 13 |
Tx
Clock B |
|
Clock
Out |
Clock
In |
|
| 3 |
Control
A |
|
Handshake
In |
Handshake
Out |
Often |
| 10 |
Control
B |
|
Handshake
In |
Handshake
Out |
Looped |
| 5 |
Indication
A |
|
Handshake
Out |
Handshake
In |
3
- 5 |
| 12 |
Indication
B |
|
Handshake
Out |
Handshake
In |
10
- 12 |
|
|
|
|
|
|
| V.35
/
EIA-449
/ RS-449 |
| |
|
|
|
|
|
| Pin |
Description |
Connector
Type |
DTE |
DCE |
Notes |
| 4 |
Tx
Data A |
37
Way D Type |
Data
Out |
Data
In |
|
| 22 |
Tx
Data B |
|
Data
Out |
Data
In |
|
| 6 |
Rx
Data A |
|
Data
In |
Data
Out |
|
| 24 |
Rx
Data B |
|
Data
In |
Data
Out |
|
| 19 |
Signal
ground |
|
|
|
|
| 17 |
Tx
Clock A |
|
Clock
Out |
Clock
In |
|
| 35 |
Tx
Clock B |
|
Clock
Out |
Clock
In |
|
| 8 |
Rx
Clock A |
|
Clock
In |
Clock
Out |
|
| 26 |
Rx
Clock B |
|
Clock
In |
Clock
Out |
|
| 17 |
Tx
Clock A |
|
Clock
In |
Clock
Out |
|
| 35 |
Tx
Clock B |
|
Clock
In |
Clock
Out |
|
|
|
|
|
|
|
| EIA-530
/ RS-530 |
| |
|
|
|
|
|
| Pin |
Description |
Connector
Type |
DTE |
DCE |
Notes |
| 2 |
Tx
Data A |
25
Way D Type |
Data
Out |
Data
In |
|
| 14 |
Tx
Data B |
|
Data
Out |
Data
In |
|
| 3 |
Rx
Data A |
|
Data
In |
Data
Out |
|
| 16 |
Rx
Data B |
|
Data
In |
Data
Out |
|
| 7 |
Signal
ground |
|
|
|
|
| 15 |
Tx
Clock A |
|
Clock
Out |
Clock
In |
|
| 12 |
Tx
Clock B |
|
Clock
Out |
Clock
In |
|
| 17 |
Rx
Clock A |
|
Clock
In |
Clock
Out |
|
| 9 |
Rx
Clock B |
|
Clock
In |
Clock
Out |
|
| 24 |
Tx
Clock A |
|
Clock
In |
Clock
Out |
|
| 11 |
Tx
Clock B |
|
Clock
In |
Clock
Out |
|
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