FDC37M607 datasheet(99/182 Pages) SMSC

99 / 182 page

Table 43 - Forward Channel Commands (HostAck Low)

Reverse Channel Commands (PeripAck Low)

D[6:0]

Run-Length Count (0-127)

(mode 0011 0X00 only)

Channel Address (0-127)

Data Compression

The ECP port supports run length encoded

(RLE) decompression in hardware and can

transfer compressed data to a peripheral. Run

length encoded (RLE) compression in hardware

is not supported. To transfer compressed data

in ECP mode, the compression count is written

to the ecpAFifo and the data byte is written to

the ecpDFifo.

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.

When a run-length count is received from a

peripheral,

the

subsequent

data

byte

replicated the specified number of times. A

run-length count of zero specifies that only one

byte of data is represented by the next data

byte, whereas a run-length count of 127

indicates that the next byte should be expanded

to 128 bytes. To prevent data expansion,

however, run-length counts of zero should be

avoided.

Pin Definition

The drivers for nStrobe, nAutoFd, nInit and

nSelectIn are open-collector in mode 000 and

are push-pull in all other modes.

ISA Connections

The interface can never stall causing the host to

hang. The width of data transfers is strictly

controlled on an I/O address basis per this

specification. All FIFO-DMA transfers are byte

wide, byte aligned and end on a byte boundary.

(The PWord value can be obtained by reading

Configuration Register A,

cnfgA, described in

the next section).

Single byte wide transfers

are

always possible with standard or PS/2

mode using program control of the control

signals.

Interrupts

The interrupts are enabled by serviceIntr in the

ecr register.

serviceIntr = 1 Disables the DMA and all of the

service interrupts.

serviceIntr = 0

Enables the selected interrupt

condition.

If the interrupting

condition is valid, then the

interrupt

generated

immediately when this bit is

changed from a “1” to a “0”.

This

can

occur

during

Programmed I/O if the number

of bytes removed or added

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