Compuprint 9058 Programmer Manual User Manual
Page 137
The Parallel Interface
A78408098-003
C.8
AckDataReq (PError)
Compatibility Mode:
Driven high to indicate that the printer has
encountered an error in the paper path. The printer
shall set nFault low whenever it sets PError high.
Negotiation Phase:
Set high to indicate 1284 support, then follows
nDataAvail (nFault).
Reverse Data
Transfer Phase:
Nibble Mode:
Data bits then 6.
Byte Mode:
same as nDataAvail (nFault)
Reverse Idle Phase:
Set high until host requests data transfer, then
follows nDataAvail (nFault).
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Xflag (Select)
Compatibility Mode:
Set high to indicate that the printer in on-line.
Negotiation Phase:
The Xflag refers to extendibility flag. Used by the
printer to reply to the requested extendibility byte
sent by the host during the negotiation phase. The
signal level is low for Nibble Mode, high for Byte
Mode.
Reverse Data
Transfer Phase:
Nibble Mode:
Data bits 1 then 5.
Byte Mode:
Same as negotiation phase.
Reverse Idle Phase:
Same as negotiation phase.
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HostBusy (nAutofd)
Compatibility Mode: Set low by host to put the printer into auto-line feed
mode.
Negotiation Phase:
Set low in conjunction with 1284 Active (NSelectIn)
being set high to request a 1284 mode.
Then set high after printer sets PtrClk (nAck) low.
Reverse Data
Transfer Phase:
Nibble
Mode:
Set low to indicate that host can receive
printer-to-host data then set high to
acknowledge receipts of that nibble.
Byte
Mode:
Same as Nibble Mode to request and
acknowledge bytes. Following a reverse
channel transfer the interface transitions
to idle phase when HostBusy (nAutoFd) is
set low and printer‘s no data available.