FDC37B779 datasheet(83/196 Pages) SMSC

83 / 196 page

IBM XT/AT COMPATIBLE, BI-DIRECTIONAL

AND EPP MODES

DATA PORT

ADDRESS OFFSET = 00H

The Data Port is located at an offset of '00H'

from the base address.

The data register is

cleared at initialization by RESET.

During a

WRITE operation, the Data Register latches the

contents of the data bus with the rising edge of

the nIOW input.

The contents of this register

are buffered (non inverting) and output onto the

PD0 - PD7 ports. During a READ operation in

SPP mode, PD0 - PD7 ports are buffered (not

latched) and output to the host CPU.

STATUS PORT

ADDRESS OFFSET = 01H

The Status Port is located at an offset of '01H'

from the base address.

The contents of this

read cycle.

The bits of the Status Port are

defined as follows:

BIT 0 TMOUT - TIME OUT

This bit is valid in EPP mode only and indicates

that a 10 usec time out has occurred on the

EPP bus.

A logic O means that no time out

error has occurred; a logic 1 means that a time

out error has been detected. This bit is cleared

by a RESET. Writing a one to this bit clears the

time out status bit. On a write, this bit is self

clearing and does not require a write of a zero.

Writing a zero to this bit has no effect.

BITS 1, 2 - are not implemented as register bits,

during a read of the Printer Status Register

these bits are a low level.

BIT 3 nERR - nERROR

The level on the nERROR input is read by the

CPU as bit 3 of the Printer Status Register. A

logic 0 means an error has been detected; a

logic 1 means no error has been detected.

BIT 4 SLCT - PRINTER SELECTED STATUS

The level on the SLCT input is read by the CPU

as bit 4 of the Printer Status Register. A logic 1

means the printer is on line; a logic 0 means it is

not selected.

BIT 5 PE - PAPER END

The level on the PE input is read by the CPU as

bit 5 of the Printer Status Register.

A logic 1

indicates a paper end; a logic 0 indicates the

presence of paper.

BIT 6 nACK - nACKNOWLEDGE

The level on the nACK input is read by the CPU

as bit 6 of the Printer Status Register. A logic 0

means that the printer has received a character

and can now accept another. A logic 1 means

that it is still processing the last character or has

not received the data.

BIT 7 nBUSY - nBUSY

The complement of the level on the BUSY input

is read by the CPU as bit 7 of the Printer Status

A logic 0 in this bit means that the

printer is busy and cannot accept a new

character. A logic 1 means that it is ready to

accept the next character.

CONTROL PORT

ADDRESS OFFSET = 02H

The Control Port is located at an offset of '02H'

from the base address. The Control Register is

initialized by the RESET input, bits 0 to 5 only

being affected; bits 6 and 7 are hard wired low.

FDC37B779 Datasheet(PDF) 83 Page - SMSC Corporation

FDC37B779 Datasheet(HTML) 83 Page - SMSC Corporation

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