FDC37C669 datasheet(97/164 Pages) SMSC

97 / 164 page

ISA IMPLEMENTATION STANDARD

This specification describes the standard ISA

interface to the Extended Capabilities Port

(ECP).

All ISA devices supporting ECP must

meet the requirements contained in this section

or the port will not be supported by Microsoft.

For a description of the ECP Protocol, please

refer to the IEEE 1284 Extended Capabilities

Port Protocol and ISA Interface Standard, Rev.

1.09, Jan.7, 1993. This document is available

from Microsoft.

Description

The port is software and hardware compatible

with existing parallel ports so that it may be

used as a standard LPT port if ECP is not

required. The port is designed to be simple and

requires a small number of gates to implement.

It does not do any "protocol" negotiation, rather

it provides an automatic high burst-bandwidth

channel that supports DMA for ECP in both the

forward and reverse directions.

Small FIFOs are employed in both forward and

reverse directions to smooth data flow and

improve the maximum bandwidth requirement.

The size of the FIFO is 16 bytes deep. The port

supports

automatic

handshake

for

the

standard parallel port to improve compatibility

mode transfer speed.

The port also supports run length encoded

(RLE) decompression (required) in hardware.

Compression

accomplished

counting

identical bytes and transmitting an RLE byte

that indicates how many times the next byte is

repeated.

Decompression

simply

intercepts

the

RLE

byte

and

repeats

the

following byte the specified number of times.

Hardware support for compression is optional.

FDC37C669 Datasheet(PDF) 97 Page - SMSC Corporation

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