W83877TF/W83877TG
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7.3 Extended Capabilities Parallel (ECP) Port
This port is software and hardware compatible with existing parallel ports, so it may be used as a
standard printer mode if ECP is not required. It provides an automatic high burst-bandwidth channel
that supports DMA for ECP in both the forward (host to peripheral) and reverse (peripheral to host)
directions.
Small FIFOs are used in both forward and reverse directions to improve the maximum bandwidth
requirement. The size of the FIFO is 16 bytes. The ECP port supports an automatic handshake for the
standard parallel port to improve compatibility mode transfer speed.
The ECP port supports run-length-encoded (RLE) decompression (required) in the hardware.
Compression is accomplished by counting identical bytes and transmitting an RLE byte that indicates
how many times the next byte is to be repeated. The hardware support for compression is optional.
For more information about the ECP Protocol, refer to the Extended Capabilities Port Protocol and ISA
Interface Standard.
7.3.1 ECP Register and Mode Definitions
NAME ADDRESS I/O ECP MODES FUNCTION
data Base+000h R/W 000-001 Data Register
ecpAFifo Base+000h R/W 011 ECP FIFO (Address)
dsr Base+001h R All Status Register
dcr Base+002h R/W All Control Register
cFifo Base+400h R/W 010 Parallel Port Data FIFO
ecpDFifo Base+400h R/W 011 ECP FIFO (DATA)
tFifo Base+400h R/W 110 Test FIFO
cnfgA Base+400h R 111 Configuration Register A
cnfgB Base+401h R/W 111 Configuration Register B
ecr Base+402h R/W All Extended Control Register
Note: The base addresses are specified by CR23, which are determined by configuration register or hardware setting.
MODE DESCRIPTION
000 SPP mode
001 PS/2 Parallel Port mode
010 Parallel Port Data FIFO mode
011 ECP Parallel Port mode
100 EPP mode (If this option is enabled in the CR9 and CR0 to select ECP/EPP mode)
101 Reserved
110 Test mode
111 Configuration mode
Note: The mode selection bits are bit 7-5 of the Extended Control Register.
