Current Loop Interface - IBM 5150 Hardware Reference Manual

+5V
I
TRANSMIT 'IACUIT
I
~
4S-"l
Tx DATA
----I~.,..-----------.,:~
:11::1
+5V
RECEIVE CIRCUIT
5.SK.I1
OPTO ISOLATOR
PIN 18
4 - - - t - . ,
: > 0 - - -
Rx DATA
PIN 25 " '_ _
+--J
+5V
Figure
23.
CURRENT LOOP INTERFACE
The voltage interface is a serial interface.
It
supports certain data and
control signals as listed below.
~
Pin 2 Transmit Data
Pin 3 Receive Data
Pin 4 Request to Send
Pin 5 Clear to Send
Pin 6 Data Set Ready
Pin 7 Signal Ground
Pin 8 Carrier Detect
Pin 20 Data Terminal Ready
Pin 22 Ring Indicate
The adapter converts these signals to/from TTL levels to EIA voltage
levels. These signals are sampled or generated by the communication
control chip. These signals can then be sensed by the system software
to determine the state of the interface or peripheral device.
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