Vocabulary
The following terms are used in this document:
assert: When a signal asserts it transitions to a "true" state, when a signal deasserts it transitions to a "false" state.
forward: Host to Peripheral communication.
reverse: Peripheral to Host communication
Pword: A port word; equal in size to the width of the LPC interface. For this implementation, PWord is always 8 bits.
1
A high level.
0
A low level.
These terms may be considered synonymous:
PeriphClk, nAck
HostAck, nAutoFd
PeriphAck, Busy
nPeriphRequest, nFault
nReverseRequest, nInit
nAckReverse, PError
Xflag, Select
ECPMode, nSelectln
HostClk, nStrobe
Reference Document: IEEE 1284 Extended Capabilities Port Protocol and ISA Interface Standard, Rev 1.14, July 14,
1993. This document is available from Microsoft.
The bit map of the Extended Parallel Port registers is:
D7
D6
D5
D4
SMSC DS – LPC47M192
Page 89
Rev. 03/30/05
DATASHEET
D3
D2
D1
D0
Note
data
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
ecpAFifo
Addr/RLE
Address or RLE field
2
dsr
nBusy
nAck
PError
Select
nFault
0
0
0
1
dcr
0
0
Direction
ackIntEn
SelectIn
nInit
autofd
strobe
1
cFifo
Parallel Port Data FIFO
2
ecpDFifo
ECP Data FIFO
2
tFifo
Test FIFO
2
cnfgA
0
0
0
1
0
0
0
0
cnfgB
compress
intrValue
Parallel Port IRQ
Parallel Port DMA
ecr
MODE
nErrIntrEn
dmaEn
serviceIntr
full
empty
Note 1
: These registers are available in all modes.
Note 2
: All FIFOs use one common 16 byte FIFO.
Note 3
: The ECP Parallel Port Config Reg B reflects the IRQ and DMA channel selected by the Configuration
Registers.
ECP IMPLEMENTATION STANDARD
This specification describes the standard interface to the Extended Capabilities Port (ECP). All LPC 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. 1.14, July 14, 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 an 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 is
accomplished by counting identical bytes and transmitting an RLE byte that indicates how many times the next byte is