Filter
Top Products
—165 —
12) If the host selected the Reverse Idle phase and new data becomes available to
be sent from the printer, the printer sets PtrClk to Low to request the host for an
interrupt. (Event 18)
13) The printer sets PtrClk back to High. (Event 19)
14) Upon receiving a request for interrupt from the printer, the host responds by
setting HostBusy (nAutoFd) to High. (Event 20)
15) Finally, the printer responds to the host by setting AckDataReq (PError) to Low,
and then the host moves to the Host Busy Data Available phase. (Event 21)
13.2.4.2 Byte Mode
In this mode, data is transferred between the printer and the host through the
procedure described below. The steps beginning from 1) are applicable when the
Negotiation phase has switched to the Host Busy Data Available phase. If the
Negotiation phase has switched to the Host Busy Data Not Available phase, the
procedure starts at step 9).
1) After the negotiations for the entry into the Byte mode are complete, the host
indicates that it is ready to receive data from the printer. This is indicated by
switching the data bus to a high-impedance state and setting HostBusy
(nAutoFd) to Low. (Events 14 and 7)
2) The printer places communication data on the data bus. (Event 15)
3) The printer sets PtrClk (nAck) to Low. (Event 9)
4) The host sets HostBusy (nAutoFd) to High to indicate that it has latched data
and received the signal in event 9. (Event 10)
5) The printer must set the four status lines as shown below. (Event 13)
• PtrBusy (Busy): Returned to the status given in the Forward mode.
• nDataAvail (nFault): Set to Low if there is data to be sent.
• AckDataReq (PError): Set to Low if there is data to be sent.
• Xflag (Select): Set to the status given during the last negotiation. (i.e.,
set to Low)
6) The printer sets PtrClk (nAck) to High (Event 10) and ends the Byte handshake.
(Event 11)
7) The host indicates that it has succeeded in receiving the data. This is indicated
by setting HostClk (nStrobe) to Low (Event 16) and then to High. (Event 17)
8) Events 10 and 16 may occur simultaneously, and events 7 and 17 may occur
simultaneously. (Such as when HostBusy and HostClk are used together.)
9) After transferring one byte of data, the printer signals to the host whether it has
more data to transfer. When there is no more data to be received by the host
from the printer, the host chooses one of three status selections:
1. Performing Termination and returning to the Compatibility mode.
2. Remaining in the Host Busy Data Not Available phase.
3. Setting HostBusy (nAutoFd) to Low and moving to the Reverse Idle phase.
(Event 7)