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Memory and I/O Usage
Parallel port controller
The registers described below are the parallel port control, data and status ports.
Data Address
Data address
The Data Address port is an 8-bit data port. A write operation to this port
port
immediately presents data to connector pins; a read operation produces the data
that was last written to it.
Status Port
The Status Port is a read-only port. A read operation to this port presents the
system micro-processor with the interrupt pending status of the connector pins as
shown below. An interrupt is pending when the interrupt status bit is set to 0.
7
6
5
4
Bits 0-2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
5/18 LS PRO HARDWARE TECHNICAL REFERENCE
Status Address
03BC
3
2
1
0
reserved
Error
SLCT
PE
ACK
BUSY
Reserved
This bit represents the current state of the printer ERROR Signal. When
this bit is set to 0 the printer has encountered an error condition.
This bit represents the current state of the select (SLCT) signal. When
this bit is set to 1 the printer has been selected.
This bit represents the state of the printer paper end (PE) signal. When
this bit is set to 1 the printer has detected the end of the paper.
This bit represents the current state of the printer acknowledge ACK
signal. When this bit is set to 0 the printer has received a character and
is ready to accept another.
This bit represents the state of the BUSY signal. When the signal is active
the printer is busy and cannot accept data.
Control address
03BD
03BE
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