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In this section, the available communications protocols will be described. See
Appendix A: Specific Printers for information relating to your printer. The
protocols supported by Word Processing are "None" and "XON/XOFF protocol".
ETX/ ACK Protocol:
Under this protocol, the system sends a "message"
consisting of a specified maximum number of characters, followed by an
"ETX" character.
After printing all characters up to the ETX, the printer
transmits an "ACK" character back to the computer, thus signalling the
processor that another message may be transmitted.
All daisy wheel and
similar printers can use this protocol; some printers require specific option
selections to activate it. See Appendix A: Specific Printers as well as the
printer manufacturer's documentation. If your printer requires this protocol,
select None as the protocol using the CONFIGUR program.
XON/XOFF Protocol: Under this protocol, the printer transmits an "XOFF"
character (DC3 ASCII code) to the computer when Word Processing should
st~p
transmitting characters.
It then transmits an "XON" character (DCl ASCII
code) when transmission may resume. XON/XOFF protocol is supported as an
alternate protocol by some daisy wheel and similar printers; we suggest using
XON/XOFF instead of ETX/ ACK.
Both communications protocols require that the Xerox 820-11 Processor be
able to receive characters from the printer as well as transmit characters to
the printer. This complicates installation when a communications protocol is
to be used. The normal method of accessing a printer, the CP/M "list device",
provides only for transmission of characters from the Xerox 820-11 Processor
to the printer.
REFERENCE
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