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Path: utzoo!utgpu!water!watmath!clyde!rutgers!sri-spam!ames!elroy!mahendo!jplgodo!wlbr!pete
From: pete@wlbr.UUCP
Newsgroups: comp.sys.m6809
Subject: Re: rs232 Needed
Message-ID: <1153@wlbr.EATON.COM>
Date: Mon, 7-Dec-87 13:38:49 EST
Article-I.D.: wlbr.1153
Posted: Mon Dec  7 13:38:49 1987
Date-Received: Sat, 12-Dec-87 16:29:58 EST
References: <15741@watmath.waterloo.edu> <3986@pucc.Princeton.EDU>
Reply-To: pete@wlbr.UUCP (0000-Pete Lyall)
Organization: Eaton IMS, Westlake Village, CA
Lines: 31

In article <3986@pucc.Princeton.EDU> EWTILENI@pucc.Princeton.EDU writes:
>> I have COCO 3 128k
> 
>That says it all right there.  You DO NOT need an RS-232 Pak, then.
> 
>The CoCo 3 can EASILY run 1200 baud out of the bitbanger port on the back
>of the computer, using halfway decent software, and if you have a well
>written program, it can do 2400 baud full duplex WITHOUT using the RS232
>Program pak.
>
>BITNET:ewtileni@pucc | ARPA:ewtileni@pucc.Princeton.EDU  | ColorVenture |

Wrong. Unless you wish to program the interval timer and poll the bit
banger (highly unsatisfactory, unless you are single-tasking) at the
designated intervals, it doesn't work worth a hoot. Reason: the
idiotic engineers set up the interrupt generation logic on the receive
data line so that an interrupt is kicked off on the *rising* edge.
This is directly opposite of the way a serial (asynch) character is
normally signalled.. that is, with a start bit (low - falling edge).
Now, if you want to clip that inverter out of the circuit and spend
some time rewriting SIO *then* serial port operations out of the bit
banger could be satisfactory, but will still be more cpu-expensive
than the RS-232 pak, or equivalent.




-- 
Pete Lyall (OS9 Users Group V.P.)             Eaton Corporation (818)-706-5693
Compuserve: 76703,4230 (OS9 Sysop) OS9 (home): (805)-985-0632 (24hr./1200 baud)
Usenet: {trwrb,scgvaxd,ihnp4,voder,vortex}!wlbr!pete   or   pete@wlbr.eaton.com