LPC47M192 datasheet(96/228 Pages) SMSC

96 / 228 page

SMSC DS – LPC47M192

Page 96

Rev. 03/30/05

DATASHEET

forward direction. To terminate while the channel is in the reverse direction, it must first be transitioned into the

forward direction.

Command/Data

ECP Mode supports two advanced features to improve the effectiveness of the protocol for some applications. The

features are implemented by allowing the transfer of normal 8 bit data or 8 bit commands.

When in the forward direction, normal data is transferred when HostAck is high and an 8 bit command is transferred

when HostAck is low.

The most significant bit of the command indicates whether it is a run-length count (for compression) or a channel

address.

When in the reverse direction, normal data is transferred when PeriphAck is high and an 8 bit command is transferred

when PeriphAck is low. The most significant bit of the command is always zero. Reverse channel addresses are

seldom used and may not be supported in hardware.

Table 45 - Channel/Data Commands supported in ECP mode

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 is accomplished by counting identical bytes and transmitting an RLE byte that indicates how many

times the next byte is to be 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 is

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-drain in mode 000 and are push-pull in all other

modes.

LPC 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 interrupts

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 from/to the FIFO does not cross the threshold.

An interrupt is generated when:

1) For DMA transfers: When serviceIntr is 0, dmaEn is 1 and the DMA TC cycle is received.

2) For Programmed I/O:

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