Compuprint 4247-L03 Programmer Manua User Manual
Page 175
Xflag (Select)
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.
Reverse Idle phase:
Set high in response to PtrClk (nAck) low pulse to re-enter reverse data transfer phase.
Is set high with 1284 Active (nSelectIn) being set low, the 1284 idle phase is being
aborted and the interface returns to Compatibility Mode.
Peripheral Logic High (+ 5V)
Set high to indicate that all other signals sourced by the printer are in valid state. Set low to indicate the printer is off.
n.a. (nInit)
Compatibility Mode:
Pulsed low in conjunction with 1284 Active low to reset the interface and force to return
to Compatibility Mode idle phase.
Negotiation Phase:
Set HIGH.
Reverse Data Transfer
Phase:
Set HIGH.
nDataAvail (NFault)
Compatibility Mode:
Set low to indicate that an internal printer error has occurred.
Negotiation Phase:
Set high to acknowledge 1284 compatibility. In Nibble or Byte Mode it is then set low to
indicate printer-to-host data is available following host setting HostBusy (nAutoFd) high.
Reverse Data Transfer
Phase:
Nibble Mode:
Set low to indicate that printer is ready to send to host. Then used to
send data bits 0 then 4.
Byte Mode:
Used to indicate that data is available.
Reverse Idle phase:
Used to indicate that data is available.
nDataAvail (NFault)
Compatibility Mode:
Set low to indicate that an internal printer error has occurred.
Negotiation Phase:
Set high to acknowledge 1284 compatibility. In Nibble or Byte Mode it is then set low to
indicate printer-to-host data is available following host setting HostBusy (nAutoFd) high.
Reverse Data Transfer
Phase:
Nibble Mode:
Set low to indicate that printer is ready to send to host. Then used to
send data bits 0 then 4.
Byte Mode:
Used to indicate that data is available.
Reverse Idle phase:
Used to indicate that data is available.
1284 Active (NSelectIn)
Compatibility Mode:
Set low by host to select printer.
Negotiation Phase:
Set high in conjunction with Host Busy being set low to request a 1284 mode.
Reverse Data Transfer
Phase:
Set high to indicate that bus direction is printer to host. Set low to terminate 1284 mode
and set bus direction host to printer.
Reverse Idle Phase:
Same as Reverse Data Transfer phase.
Appendix B. Interfaces
159