Control Data Corporation INFORMATION SYSTEMS TERMINAL II Hardware Maintenance Manual page 82

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• Status Bit 7, PLATO Channel Carrier Detected - This
bit, active low, indicates that the Carrier Detect
signal line is active at the PLATO communication
interface connector (RJl-8) or that the board con-
nector signal AJ5-9 is an RS-232-C On or a TTL high.
Parallel Channel Interface
The parallel channel interface provides a means for the
terminal to communicate and exchange information with 16
addressable, external devices. Data is exchanged in
bit-para11e1/byte-seria1 mode, with the terminal processor
controlling the interface. The discussion here focuses on
the signals and timing.
Signals
All voltage levels on the parallel channel are TTL compati-
ble and defined as follows:
• Terminal output
Data Lines
+2.0
V
to +5.25
V
=
High
+0.0
V
to +0.5
V
=
Low
• Terminal input
Data Lines
+2.0
V
to +5.25
V
=
High
-0.25
V
to +0.8
V
=
Low
Others
+2.4
V
to +5.25
V
=
High
+0.0 V to 0.4 V
= Low
Others
+2.4
V
to 5.25
V
=
High
-0.25 V to +0.8 V
=
Low
The signal definitions for the parallel channel interface
are as follows:
4-20
• Data Line 0 through Data line
7 -
These eight bidi-
rectional lines carry the information from the ter-
minal to the external devices or vice versa,
depending on the setting of the control signals
external write and external read. The kind of
informat ion carr ied is def ined by the sett ing of .. the
five address lines which determine the device being
communicated with and the function taking place.
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