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Byte Mode
Inthis mode, data istransferred between theprinterandthe hostthrough theprocedure described below.
Thestepsbeginningfrom(1)areapplicablewhentheNegotiationphasehasswitchedtotheHostBusyDataAvailablephase.If
the Negotiation phase hasswitched to theHost BusyData Not Available phase, the procedurestartsat step (9).
(1) After thenegotiationsfor the entryinto the Byte mode arecomplete, thehost indicatesthat itis readyto receivedata from
the printer.This isindicated by switchingthe data busto ahigh-impedancestateandsetting HostBusy (nAutoFd)toLow.
(Events 14 and7)
(2) The printerplacescommunication data onthe data bus. (Event 15)
(3) The printersets PtrClk (nAck) toLow.(Event 9)
(4) The host sets HostBusy (nAutoFd)toHightoindicate that it has latched data andreceivedthesignal inEvent 9. (Event 10)
(5) The printermust set the four status lines asshownbelow. (Event 13)
•PtrBusy(Busy): Returnedtothe status given in theForwardmode.
•nDataAvail (nFault):Set to Lowifthere isdata tobe sent.
•AckDataReq(PError): Set to Lowifthere isdata tobe sent.
•Xflag (Select):Set to the status given during the last negotiation(i.e., set to Low).
(6) The printersets PtrClk (nAck) toHigh(Event 10)andends the Byte handshake. (Event 11)
(7) The host indicatesthat ithassucceeded in receivingthe data. Thisisindicated by settingHostClk (nStrobe) toLow (Event
16)and then toHigh.(Event 17)
(8)Events10and16mayoccursimultaneously,and Events7 and17mayoccur simultaneously.(Such as whenHostBusyand
HostClkare used together.)
(9) After transferring onebyte of data, the printer signalstothehost whether ithas more data totransfer.When there isno
more data tobereceived by thehost fromtheprinter,thehost chooses one ofthree status selections:
1.Performing Termination andreturning to theCompatibility mode.
2.Remaining inthe Host BusyData Not Available phase.
3.SettingHostBusy(nAutoFd) toLow andmovingto theReverse Idle phase. (Event 7)
(10) Whenmore data isto bereceived fromthe printer,thehost chooses oneof three status selections:
1.SettingHostBusy(nAutoFd) toLow andindicatingthat thehostis ready toreceive.
2.Remaining inthe Host BusyData Available phase.
3.Performing Termination andreturning to theCompatibility mode.
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