PC97307 datasheet(114/218 Pages) NSC

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Parallel Port (Logical Device 4)

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Bit 5 - PE Status

This bit reflects the current state of the printer paper end

signal (PE). The printer sets this bit high when it detects

the end of the paper.

0 - Printer has paper.

1 - End of paper in printer.

Bit 6 - ACK Status

This bit reflects the current state of the printer acknowl-

edge signal, ACK. The printer pulses this signal low af-

ter it has received a character and is ready to receive

another one. This bit follows the state of the ACK pin.

0 - Character reception complete.

1 - No character received .

Bit 7 - Printer Status

This bit reflects the current state of the printer BUSY sig-

nal. The printer sets this bit low when it is busy and can-

not accept another character.

This bit is the inverse of the (BUSY/WAIT) pin.

0 - Printer busy.

1 - Printer not busy.

6.2.4

SPP Control Register (CTR), Offset 02h

The control register provides all the output signals that con-

trol the printer. Except for bit 5, it is a read and write register.

Normally when the Control Register (CTR) is read, the bit

values are provided by the internal output data latch. These

bit values can be superseded by the logic level of the STB,

AFD, INIT, and SLIN signals, if these signals are forced high

or low by external voltage. To force these signals high or

low the corresponding bits should be set to their inactive

states (e.g., AFD, STB and SLIN should all be 0; INIT

should be 1).

Section 6.3.10 describes the transfer operations that are

possible in EPP modes.

FIGURE 6-3. CTR Register Bitmap (SPP Mode)

Bit 0 - Data Strobe Control

Bit 0 directly controls the data strobe signal to the printer

via the STB signal.

This bit is the inverse of the STB signal.

76543210

Reset

Required

SPP Control Register

(CTR)

Offset 02h

Printer Initialization Control

Interrupt Enable

Direction Control

Reserved

Data Strobe Control

Parallel Port Input Control

Automatic Line Feed Control

Bit 1 - Automatic Line Feed Control

This bit directly controls the automatic line feed signal to

the printer via the AFD pin. Setting this bit high causes

the printer to automatically feed after each line is print-

ed.

This bit is the inverse of the AFD signal.

0 - No automatic line feed. (Default)

1 - Automatic line feed

Bit 2 - Printer Initialization Control

This bit directly controls the signal to initialize the printer

via the INIT pin. Setting this bit to low initializes the print-

er.

The value of the INIT signal reflects the value of this bit.

The default setting of 1 on this bit prevents printer initial-

ization in SPP mode, and enables ECP mode after re-

set.

0 - Initialize Printer.

1 - No action (Default).

Bit 3 - Select Input Signal Control

This bit directly controls the select in signal to the printer

via the SLIN signal. Setting this bit high selects the print-

er.

It is the inverse of the SLIN signal.

This bit must be cleared to 0 before enabling the EPP or

ECP mode.

0 - Printer not selected. (Default)

1 - Printer selected and online.

Bit 4 - Interrupt Enable

Bit 4 controls the interrupt generated by the ACK signal.

Its function changes slightly depending on the parallel

port mode selected.

In ECP mode, this bit should be set to 0.

In the following description, IRQx indicates an interrupt

allocated for the parallel port.

0 - In SPP Compatible, SPP Extended and EPP

modes, IRQx is ﬂoated. (Default)

1 - In SPP Compatible mode, IRQx follows ACK transi-

tions.

In SPP Extended mode, IRQx is set active on the trail-

ing edge of ACK.

In EPP modes, IRQx follows ACK transitions, or is

set when an EPP time-out occurs.

Bit 5 - Direction Control

This bit determines the direction of the parallel port in

SPP Extended mode only. In the (default) SPP Compat-

ible mode, this bit has no effect, since the port functions

for output only.

This is a read/write bit in EPP modes. In SPP modes it

is a write only bit. A read from it returns 1.

In SPP Compatible mode and in EPP modes it does not

control the direction. See Table 6-4.

0 - Data output to PD7-0 in SPP Extended mode dur-

ing write cycles. (Default)

1- Data input from PD7-0 in SPP Extended mode dur-

ing read cycles.

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