BIT 0 STROBE - STROBE
This bit is inverted and output onto the nSTROBE output.
IOR causes an EPP ADDRESS READ cycle to be
performed and the data output to the host CPU, the
deassertion of ADDRSTB latches the PData for the
duration of the IOR cycle. This register is only available
in EPP mode.
BIT 1 AUTOFD - AUTOFEED
This bit is inverted and output onto the nAUTOFD output.
A logic 1 causes the printer to generate a line feed
after each line is printed. A logic 0 means no autofeed.
EPP DATA PORT 0
ADDRESS OFFSET = 04H
BIT 2 nINIT - nINITIATE OUTPUT
This bit is output onto the nINIT output without inversion.
The EPP Data Port 0 is located at an offset of '04H' from
the base address. The data register is cleared at
initialization by RESET. During a WRITE operation, the
contents of DB0-DB7 are buffered (non inverting) and
output onto the PD0 - PD7 ports, the leading edge of
nIOW causes an EPP DATA WRITE cycle to be
performed, the trailing edge of IOW latches the data for
the duration of the EPP write cycle. During a READ
operation, PD0 - PD7 ports are read, the leading edge of
IOR causes an EPP READ cycle to be performed and the
data output to the host CPU, the deassertion of
DATASTB latches the PData for the duration of the IOR
cycle. This register is only available in EPP mode.
BIT 3 SLCTIN - PRINTER SELECT INPUT
This bit is inverted and output onto the nSLCTIN output.
A logic 1 on this bit selects the printer; a logic 0 means
the printer is not selected.
BIT 4 IRQE - INTERRUPT REQUEST ENABLE
The interrupt request enable bit when set to a high level
may be used to enable interrupt requests from the
Parallel Port to the CPU. An interrupt request is
generated on the IRQ port by a positive going nACK
input. When the IRQE bit is programmed low the IRQ is
disabled.
EPP DATA PORT 1/ADDRESS OFFSET = 05H
BIT 5 PCD - PARALLEL CONTROL DIRECTION
Parallel Control Direction is valid in extended mode only
(CR#1<3>=0). In printer mode, the direction is always
out regardless of the state of this bit. In bi-directional
mode, a logic 0 means that the printer port is in output
mode (write); a logic 1 means that the printer port is in
input mode (read).
The EPP Data Port 1 is located at an offset of '05H' from
the base address. Refer to EPP DATA PORT 0 for a
description of operation. This register is only available in
EPP mode.
EPP DATA PORT 2/ADDRESS OFFSET = 06H
Bits 6 and 7 during a read are a low level, and cannot be
written.
The EPP Data Port 2 is located at an offset of '06H' from
the base address. Refer to EPP DATA PORT 0 for a
description of operation. This register is only available in
EPP mode.
EPP ADDRESS PORT
ADDRESS OFFSET = 03H
EPP DATA PORT 3
The EPP Address Port is located at an offset of '03H'
from the base address. The address register is cleared
at initialization by RESET. During a WRITE operation, the
contents of DB0-DB7 are buffered (non inverting) and
output onto the PD0 - PD7 ports, the leading edge of
nIOW causes an EPP ADDRESS WRITE cycle to be
performed, the trailing edge of IOW latches the data for
the duration of the EPP write cycle. During a READ
operation, PD0 - PD7 ports are read, the leading edge of
ADDRESS OFFSET = 07H
The EPP Data Port 3 is located at an offset of '07H' from
the base address. Refer to EPP DATA PORT 0 for a
description of operation. This register is only available in
EPP mode.
EPP 1.9 OPERATION
When the EPP mode is selected in the configuration
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