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From: ge@kunivv1.sci.kun.nl (Ge' Weijers)
Newsgroups: comp.sys.handhelds
Subject: Re: HP48 serial cable
Message-ID: <1180@kunivv1.sci.kun.nl>
Date: 15 Mar 90 10:30:29 GMT
References: <2608@gmu90x.gmu.edu>
Organization: University of Nijmegen, The Netherlands.
Lines: 33

peraino@gmu90x.gmu.edu (peraino) writes:


>>From sterling@cbmvax Fri Mar  9 09:47:01 1990
>>
>>
>>  I called HP Service and get the following info... use it at your own risk!
>>  
>>  Pin       Function                RS-232 equiv
>>    1       Chassis Ground          pin 1
>>    2       Txd                     pin 2
>>    3       Rxd                     pin 3
>>    4       Signal Ground           pin 7


>     This got me to wondering; The serial interface (cable) was designed
>for going from hp48 to a pc, mac, etc. Basically, serial to serial.
>This implies that what HP is selling is a null-modem cable with pins
>2 & 3 reversed on the other end. This would mean that you CANNOT
>use HP's cable to go from the 48 to a real modem. Anybody have any info.
>on this?

You can do it, but it needs a weird conversion plug. You need to set the
modem to ignore all handshaking, but that's all. I did this for a comparable
setup, using a Z88-PC cable and this conversion plug, a male-to-male 
null-modem (technically it's not a nullmodem because the handshake lines
are connected in a weird way. I'll post the 'schematic' tomorrow.

Ge' Weijers
Ge' Weijers                                    Internet/UUCP: ge@cs.kun.nl
Faculty of Mathematics and Computer Science,   (uunet.uu.net!cs.kun.nl!ge)
University of Nijmegen, Toernooiveld 1         
6525 ED Nijmegen, the Netherlands              tel. +3180612483 (UTC-2)