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The following figure is a block diagram of the parallel portion of
the adapter.
Address
Address
Bus
Decode
-
-
-
Interrupt
-
Data
Data
Output
Bus
~
Buffer
.
...
-- -
Control
--
-
. ..
-
-
-
..
-
Buffer
Control
Signals
25-Pln 0
Connector
Data
r---
Wrap
...
Buffer
..
-
-
Control Wrap
Output
..
...
and
~
-
-
Buffer
~
Signal Input
Parallel Portion Block Diagram
Printer Application
The following discusses the use of the parallel portion of the
adapter to connect to a parallel printer. Hexidecimal addresses in
this section begin with an X, which is replaced with a 3 to indicate
port 1, or a 2 to indicate port 2.
Data Latch (Hex X78, X7C)
Writing to this address causes data to be stored in the printer's
data buffer. Reading this address sends the contents of the
printer's data buffer to the system microprocessor.
Printer Controls (hex X7 A, X7E)
Printer control signals are stored at this address to be read by the
system microprocessor. The following are bit definitions for this
byte.
20 Serial/Parallel Adapter
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