EXTENDED CAPABILITIES PARALLEL PORT
PWord A port word; equal in size to the width of the
ISA interface. For this implementation, PWord
is always 8 bits.
ECP provides a number of advantages, some of which
are listed below. The individual features are explained in
greater detail in the remainder of this section.
1
0
A high level.
A low level.
•
High performance half-duplex forward and reverse
channel
These terms may be considered synonymous:
•
•
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
•
•
•
•
•
•
•
•
•
PeriphClk, nAck
HostAck, nAutoFd
PeriphAck, Busy
nPeriphRequest, nFault
nReverseRequest, nInit
nAckReverse, PError
Xflag, Select
ECPMode, nSelectln
HostClk, nStrobe
•
•
•
•
•
Vocabulary
The following terms are used in this document:
Reference Document:
assert When
"true" state, when
transitions to a "false" state.
a
signal asserts it transitions to a
IEEE 1284 Extended Capabilities Port Protocol and ISA
a
signal deasserts it
Interface Standard, Rev 1.09, Jan 7, 1993.
document is available from Microsoft.
This
forward Host to Peripheral communication.
reverse Peripheral to Host communication.
The bit map of the Extended Parallel Port registers is:
D7
D6
D5
D4
D3
D2
D1
D0
Note
data
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
ecpAFifo Addr/RLE
Address or RLE field
Select nFault
ackIntEn SelectIn
2
1
1
2
2
2
dsr
nBusy
0
nAck
0
PError
0
0
0
Direction
dcr
nInit
autofd strobe
cFifo
ecpDFifo
tFifo
Parallel Port Data FIFO
ECP Data FIFO
Test FIFO
cnfgA
cnfgB
ecr
0
0
0
0
1
0
0
0
0
0
0
0
0
0
compress intrValue
MODE
nErrIntrEn
serviceIntr
dmaEn
full
empty
Note 1: These registers are available in all modes.
Note 2: All FIFOs use one common 16 byte FIFO.
ISA IMPLEMENTATION STANDARD
the Extended Capabilities Port (ECP). All ISA devices
supporting ECP must meet the requirements contained in
this section or the port will not be supported by Microsoft.
This specification describes the standard ISA interface to
95
SMSC [ SMSC CORPORATION ]
