LPC47M172_07 SMSC [SMSC Corporation], LPC47M172_07 Datasheet - Page 107

• Manufacturer Part Number: LPC47M172_07
• Description: Advanced I/O Controller with Motherboard GLUE Logic
• Manufacturer: SMSC [SMSC Corporation]

7.15
7.16
7.17
7.18
SMSC LPC47M172
Termination from ECP Mode
Termination from ECP Mode is similar to the termination from Nibble/Byte Modes. The host is permitted to
terminate from ECP Mode only in specific well-defined states. The termination can only be executed while
the bus is in the 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.
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.
Table 7.9 - Channel/Data Commands supported in ECP mode
Reverse Channel Commands (PeripAck Low)
Forward Channel Commands (HostAck Low)
D7
0
1
DATASHEET
Run-Length Count (0-127)
(mode 0011 0X00 only)
Channel Address (0-127)
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Advanced I/O Controller with Motherboard GLUE Logic
SMSC/Non-SMSC Register Sets (Rev. 01-11-07)
Datasheet