PC97338 datasheet(137/221 Pages) NSC

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4.4.6

ECP Address FIFO (AFIFO)

Offset 000h

The ECP Address FIFO Register (AFIFO) is write

only. In the forward direction (bit 5 of DCR is 0) a byte

written into this register is pushed into the FIFO and

tagged as a command.

Reading this register returns undefined contents. Writ-

ing to this register in a backward direction (bit 5 of DCR

is 1) has no effect and the data is ignored.

FIGURE 78. AFIFO Register Bitmap

4.4.7

ECP Status Register (DSR),

Offset 001h

This read-only register displays device status. Writes

to this DSR have no effect and the data is ignored.

This register should not be confused with the DSR

FIGURE 79. ECP DSR Register Bitmap

Bits 0 - 2 - Reserved

These bits are reserved and are always 1.

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

printer sets this signal high when it is online and

selected

0 - Printer not selected (default)

1 - Printer selected and online

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 signal.

0 - Printer is busy (cannot accept another charac-

ter now)

1 - Printer not busy - ready for another character.

4.4.8

ECP Control Register (DCR),

Offset 002h

Reading this register returns the register content (not

the pin values, as in SPP mode).

FIGURE 80. DCR Register Bitmap

321

Reset

Required

ECP Address Register

(AFIFO)

Offset 000h

Bits 7-5 of ECR = 011

321

Reset

Required

ECP Status Register

(DSR)

Offset 001h

Reserved

SLCT Status

PE Status

ACK Status

Printer Status

Reserved

ERR Status

All ECP Modes

321

Reset

Required

ECP Control

Offset 002h

Printer Initialization Control(INIT)

Interrupt Enable

Direction Control

Reserved

Data Strobe Control

Automatic Line Feed Control

Parallel Port Input Control

All ECP Modes

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