EXTENDED CAPABILITIES PARALLEL PORT
ECP provides a number of advantages, some of
Pword: A port word; equal in size to the width of
the ISA interface. For this
which are listed below. The individual features are
explained in greater detail in the remainder of this
section.
implementation, PWord is always 8 bits.
A high level.
1
0
A low level.
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High performance half-duplex forward and
reverse channel
Interlocked handshake, for fast reliable
transfer
Optional single byte RLE compression for
improved throughput (64:1)
Channel addressing for low-cost peripherals
Maintains link and data layer separation
Permits the use of active output drivers
Permits the use of adaptive signal timing
Peer-to-peer capability
These terms may be considered synonymous:
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PeriphClk, nAck
HostAck, nAutoFd
PeriphAck, Busy
nPeriphRequest, nFault
nReverseRequest, nInit
nAckReverse, PError
Xflag, Select
ECPMode, nSelectln
HostClk, nStrobe
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Vocabulary
The following terms are used in this document:
Reference Document:
Capabilities Port Protocol and ISA Interface
IEEE 1284 Extended
Standard, Rev 1.14, July 14, 1993.
document is available from Microsoft.
This
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
The bit map of the Extended Parallel Port
registers is:
D7
PD7
D6
D5
D4
D3
D2
D1
D0
Note
data
PD6
PD5
PD4
PD3
PD2
PD1
PD0
ecpAFifo
dsr
Addr/RLE
nBusy
0
Address or RLE field
2
1
1
2
2
2
nAck
0
PError
Select
ackIntEn
nFault
0
0
0
dcr
Direction
SelectIn
nInit
autofd
strobe
cFifo
ecpDFifo
tFifo
Parallel Port Data FIFO
ECP Data FIFO
Test FIFO
cnfgA
cnfgB
ecr
0
0
0
1
0
0
0
0
compress
intrValue
MODE
Parallel Port IRQ
nErrIntrEn
Parallel Port DMA
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 DRQ selected by the Configuration
Registers.
This specification describes the standard ISA
interface to the Extended Capabilities Port (ECP).
ISA IMPLEMENTATION STANDARD
94
SMSC [ SMSC CORPORATION ]
