- 450 -
Termination
Terminationis the process ofreturning toCompatibility mode fromthe Nibble or Byte modes. Whenperforming Termination,
the hostsetsthe signalsasfollows:
•IEEE 1284Active (nSelectln): Low
•HostBusy(nAutoFd):High (Event 22)
There are twomethodsofTermination:
(1) Termination through ahandshake between thehost andtheprinter
(2) Immediate termination
(1) Termination through ahandshake between thehost andtheprinter:
WhenswitchingfromReversemodetoCompatibilitymode,thisterminationmethodcanbeusediftheinterfaceisactivated
(IEEE 1284 Active: High) andEvent 22 hastaken place.
1)TheprinterrespondstoIEEE 1284Active bysetting PtrBusy(Busy) andnDataAvail (nFault) toHigh. (Event 23)
2)Theprinterthen inverts Xflag (Select)and sets PtrClk (nAck) to Low. (Event 24)
3)Thehost sets HostBusy (nAutoFd)toLow.(Event25)
4)TheprinterreturnsnDataAvail(nFault),Xflag(Select),andAckDataReq(PError)tothestatusgivenintheCompatibility
mode,andsets PtrClk (nAck) toHigh.(Events26 and27)
5)Thehost sets HostBusy (nAutoFd)toHightoterminate the handshakeandreturn theinterface to theCompatibility
Mode Idle phase. (Event 28)
6)Theprinterchanges PtrBusy(Busy) tobe able toreceive data from thehost.
(2) Immediate termination:
1)Iftheinterface is deactivated (IEEE 1284Active: Low) without Event 22 having taken place, theprinterimmediately
performsTermination. In thistermination, the dataisnot guaranteed,and the printer switchesthe databusfrom output
to inputwithin 1µsec.
Inthe ReverseIdle phase, theprintercannotify the host that it hasdata totransfer to the host.The notificationmay
occur simultaneouslywith terminationin order for the hosttomove fromthe Idle phase tothe Compatibility mode.
Ifthe printer hasdata tosend, itinitiates theInterrupt phase indicated by Events 8and 9.In thiscase, if 1284- Active
(nSelectIn) was setto Lowbefore HostBusy(nAutoFd)changed from HightoLow,the printer interpretsthat thehost
has switchedtothe Termination phase, andthen completes thenormal terminationthrough handshaking.
To Next Page
Loading...
