Dial Operation; Synchronous Mode With A Switched Half-Duplex Modern - IBM 3704 Reference Manual

Set Monitor Initiate
for OS .
Tl
·r~
T
Xmit
Data
Terminal Ready
Data Connection Mode
Data Set Ready
Request to Send
I
1111-1
Modem I+-
Dependent
I
Clear to Send
Transmit Data
Transmit Clock
Turn-around
Mode
I
-+I~
I
Modem
Dependent
Disable
Mode
Receive Data
n n
r l
_ _ _ _ _ _ _ _ _ _ _ _ _ _ !
LJ U
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Receive Clock
Figure 10. Synchronous Mode with a Switched Half-Duplex Modem
Dial Operation
Figures 1 l and 12 show an example of an automatic call operation. Timings
depend upon the IBM 3704 and 3705 program activity, the type of scanner, the
number of lines being serviced, the line speed, and the automatic calling unit
(ACU).
A set mode state (PCF-1) is invalid to an auto dial interface, and results in a
feedback error (LCD-F).
During an auto dial operation, error conditions are not checked by the hardware.
Failures in the automatic calling unit, such as PWI inactive, must
be
detected by
the program.
If Data Line Occupied (DLO) is active before the IBM 3704 and 3705 raise Call
Request (CRQ), an auto dial operation cannot be initiated. Therefore, the
program must examine the ICW for an auto dial line before beginning an auto dial
operation.
38 IBM 3704 and 3705 Communications Controllers Original Equipment Manufacturers' Information