pc87317vul National Semiconductor Corporation, pc87317vul Datasheet - Page 148

• Manufacturer Part Number: pc87317vul
• Description: Pc87317vul/pc97317vul Superi/o Plug And Play Compatible With Acpi Compliant Controller/extender
• Manufacturer: National Semiconductor Corporation

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6.5.6
Reading this register returns the register content (not the
signal values, as in SPP mode).
Bit 0 - Data Strobe Control
Bit 1 - Automatic Line Feed Control
Bit 2 - Printer Initialization Control
Bit 3 - Parallel Port Input Control
Bit 4 - Interrupt Enable
1
7
Bit 0 directly controls the data strobe signal to the printer
via the STB signal. It is the inverse of the STB signal.
0: The STB signal is inactive in all modes except 010
1: In all modes, STB is active.
This bit directly controls the automatic feed XT signal to
the printer via the AFD signal. Setting this bit high caus-
es the printer to automatically feed after each line is
printed. This bit is the inverse of the AFD signal.
In mode 011, AFD is activated by both ECP hardware
and by software using this bit.
0: No automatic line feed. (Default)
1: Automatic line feed.
Bit 2 directly controls the signal to initialize the printer via
the INIT signal. Setting this bit to low initializes the print-
er. The INIT signal follows this bit.
0: Initialize printer. (Default)
1: Printer initialized.
This bit directly controls the select input device signal to
the printer via the SLIN signal. It is the inverse of the
SLIN signal.
This bit must be set to 1 before enabling the EPP or
ECP modes.
0: The printer is not selected.
1: The printer is selected.
Bit 4 enables the interrupt generated by the ACK signal.
In ECP mode, this bit should be set to 0. This bit does
not float the IRQ pin.
0: Masked. (Default)
1: Enabled.
Reserved
1
6
and 011. In these modes, it may be active or inac-
tive as set by the software.
ECP Control Register (DCR)
Reserved
0
5
FIGURE 6-20. DCR Register Bitmap
Direction Control
0
4
Interrupt Enable
0
3
Parallel Port Input Control
0
2
Printer Initialization Control
0
1
Automatic Line Feed Control
0
0
Reset
Required
Data Strobe Control
Register (DCR)
ECP Control
Parallel Port (Logical Device 4)
Offset 002h
148
Bit 5 - Direction Control
Bits 7,6 - Reserved
6.5.7
The Parallel Port FIFO (CFIFO) register is write only. A byte
written to this register by PIO or DMA is pushed into the
FIFO and tagged as data.
Reading this register has no effect and the data read is un-
defined.
6.5.8
This bi-directional FIFO functions as either a write-only de-
vice when bit 5 of DCR is 0, or a read-only device when it is
1.
In the forward direction (bit 5 of DCR is 0), a byte written to
the ECP Data FIFO (DFIFO) register by PIO or DMA is
pushed into the FIFO and tagged as data. Reading this reg-
ister when set for write-only has no effect and the data read
is undefined.
In the backward direction (bit 5 of DCR is 1), the ECP auto-
matically issues ECP read cycles to fill the FIFO.
Reading from this register pops a byte from the FIFO. Writ-
ing to this register when it is set for read-only has no effect,
and the data written is ignored.
0
7
This bit determines the direction of the parallel port.
This is a read/write bit in EPP mode. In SPP mode it is
a write only bit. A read from it returns 1. In SPP Compat-
ible mode and in EPP mode it does not control the direc-
tion. See TABLE 6-4 "SPP DTR Register Read and
Write Modes" on page 139.
The ECP drives the PD7-0 pins in the forward direction,
but does not drive them in the backward direction.
This bit is readable and writable. In modes 000 and 010
the direction bit is forced to 0, internally, regardless of
the data written into this bit.
0: ECP drives forward in output mode. (Default)
1: ECP direction is backward.
These bits are reserved and are always 1.
0
D7
6
Parallel Port Data FIFO (CFIFO) Register
ECP Data FIFO (DFIFO) Register
FIGURE 6-21. CFIFO Register Bitmap
0
D6
5
D5
0
4
D4
0
Bits 7-5 of ECR = 010
3
D3
0
2
Data Bits
D2
0
1
D1
0
0
Reset
Required
D0
Parallel Port FIFO
Register (CFIFO)
Offset 400h