info-mac@utcsrgv.UUCP (info-mac) (05/08/84)
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? -------