User`s manual

11) If the host selected the Host Busy Data Available phase and set HostBusy (nAutoFd) to Low, the

printer repeats the steps from 2) onwards.

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)

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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). If this is the case, the host determines the

current status by checking:

1. Whether there is more data to be sent from the printer to the host;

And whether data can be transferred from the host to the printer.