PC87309VLJ datasheet(89/192 Pages) NSC

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Parallel Port (Logical Device 1)

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Bit 3 - ERR Status

This bit reflects the status of the ERR signal.

0: Printer error.

1: No printer error.

Bit 4 - SLCT Status

This bit reflects the status of the Select signal. The print-

er sets this signal high when it is online and selected

0: Printer not selected. (Default)

1: Printer selected and on-line.

Bit 5 - PE Status

This bit reflects the status of the Paper End (PE) signal.

0: Paper not ended.

1: No paper in printer.

Bit 6 - ACK Status

This bit reflects the status of the ACK signal. This signal

is pulsed low after a character is received.

0: Character received.

1: No character received. (Default)

Bit 7 - Printer Status

This bit reflects the inverse of the state of the BUSY sig-

nal.

0: Printer is busy (cannot accept another character

now).

1: Printer not busy (ready for another character).

4.5.6

ECP Control Register (DCR)

Reading this register returns the register content (not the

signal values, as in SPP mode).

Bit 0 - Data Strobe Control

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

and 011. In these modes, it may be active or inac-

tive as set by the software.

1: In all modes, STB is active.

Bit 1 - Automatic Line Feed Control

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 - Printer Initialization Control

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: No action

Bit 3 - Parallel Port Input Control

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 - Interrupt Enable

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.

Bit 5 - Direction Control

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 4-4 "SPP DTR Register Read and

Write Modes" on page 80.

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.

Bits 7,6 - Reserved

These bits are reserved and are always 1.

76543210

Reset

Required

ECP Control

Offset 002h

Printer Initialization Control

Interrupt Enable

Direction Control

Reserved

Data Strobe Control

Automatic Line Feed Control

Parallel Port Input Control

PC87309VLJ 数据表(PDF) 89 Page - National Semiconductor (TI)

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