Nonswitched Asynchronous Line Activation - IBM 3708 Description

EIA 422A Definition
The EIA 422A circuitry uses balanced voltage circuitry employing a pair of
conductors for receiving and transmitting data. Two pins are called out for both
transmit data and receive data.
Pin 1 -
Frame Ground
Pin
7 - Signal Ground
Pin
13 - Select EIA 422A
(3708
input) When pin 13 is tied to signal ground
(pin
7),
it selects EIA 422A for this
3708
port.
Pin 12 - (-)
TxD - (-) Transmit Data
(3708
output)
Pin
14 - (
+ )
TxD - (
+ )
Transmit Data
(3708
output)
Pin 16 - (-)
RxD - (-) Receive Data
(3708
input)
Pin 19 - (
+ )
RxD - (
+ )
Receive Data
(3708
input).
Interface Leads during Port Activation
The following figures show the states of the interface leads during port activation for
the various line types that the
3708
supports.
Nonswitched Asynchronous Line Activation
1
2
DTR
_---'I
3
DSR _ _ _
---'I
1
3708 enables port.
2
3708 raises OTR and waits for OSR.
3
OSR becomes active. Connection is established.
The time period the 3708 waits for OSR after activating OTR is three seconds.
Figure 2-10. Nonswitched Asynchronous Line Activation
Chapter 2. 3708 Operation
2-21