Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE - Manual (Page 44)

Choosing Module Features
Chapter 3
3Ć2
Pin Signal
2
3
4
5
7
transmit data
receive data
request to send
clear to send
ground
Refer to Table 2.A for a detailed listing of RS-232-C pin functions.
Table 2.A
RSĆ232ĆC Connector Pin Functions
Pin
No Signal Name
EIA
Circuit Source Functions
2 Transmitted Data BA DTE Data Transfer to
1771ĆDA (DCE)
3 Received Data BB 1771ĆDA
(DCE)
Data Transfer to DTE
4 Request to Send CA DTE Tells the 1771ĆDA data is
transmitted.
5 Clear to Send CB 1771ĆDA
(DCE)
Tells DTE that data is
transmitted. Enabled only
if pin 4 is ĆVdc (off).
6 Data Set Ready CC 1771ĆDA
(DCE)
Tells DTE that 1771ĆDA
(DCE) is ready.
7 Signal Ground AB Ć Common ground for all
signals thru interface port
on 1771ĆDA.
8 Receive Line Signal
Detector
CF 1771ĆDA
(DCE)
Tied to +12V dc
20 Data Terminal Ready CD DTE Tells 1771ĆDA (DCE) that
DTE is ready. Must be
+V dc to send or receive.
Current Loop
Use the current loop for communicating up to approximately 500 cable
feet between your ASCII device and ASCII module. A current loop has
high immunity to errors caused by electrical noise, has no signal
attenuation, eliminates ground loops, and is low cost.
A current loop is a loop that carries current (generally 20mA) between
electronic equipment by means of a twisted pair of wires. A transmitting
device in the loop transmits digital signals by interrupting the current