🚀 go-pugleaf

Date: Sun 6 May 84 22:37:46-PDT
From: Tony Siegman  <uw-beaver!SIEGMAN@SU-SIERRA.ARPA>
Subject: Query Re RS-232 Interface and Handshaking
To: info-mac@SUMEX-AIM.ARPA

     I want to drive a Hewlett-Packard 7470A Graphics Plotter that has
an RS-232 interface from the Mac running either Microsoft Basic or
MacBasic, and would appreciate information on what handshaking support
is available from the RS-232 port on the Mac when using either of these
programs.

     The hp 7470A thinks it's a terminal, and I appreciate that a null
modem cable which interchanges pins 2 and 3 between Mac and the plotter
will probably be required.  However, the plotter can then be set to
do either hardwire handshaking via pin 20 (DTR), if the computer it's
talking to monitors that signal; or Xon-Xoff handshaking.

     After a certain amount of grief in attempting to interface this
plotter to a TRS-80 Model 100, I found that the Model 100 does not
monitor the hardwire handshake when running Basic (though you can PEEK
at that pin and monitor it yourself, if you want to); but the Xon-Xoff
protocol does work automatically, if you OPEN the comm line right.

     Can anyone tell me what I'll encounter with the Mac?


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