Choosing Module Features
Chapter 3
32
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
RS232C Connector Pin Functions
Pin
No
Signal Name
EIA
Circuit
Source
Functions
2
Transmitted Data
BA
DTE
Data Transfer to
1771DA (DCE)
3
Received Data
BB
1771DA
(DCE)
Data Transfer to DTE
4
Request to Send
CA
DTE
Tells the 1771DA data is
transmitted.
5
Clear to Send
CB
1771DA
(DCE)
Tells DTE that data is
transmitted. Enabled only
if pin 4 is Vdc (off).
6
Data Set Ready
CC
1771DA
(DCE)
Tells DTE that 1771DA
(DCE) is ready.
7
Signal Ground
AB
Common ground for all
signals thru interface port
on 1771DA.
8
Receive Line Signal
Detector
CF
1771DA
(DCE)
Tied to +12V dc
20
Data Terminal Ready
CD
DTE
Tells 1771DA (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
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