Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!uunet!mcsun!ukc!acorn!moncam!emmo
From: emmo@moncam.co.uk (Dave Emmerson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Help on programming of the Serial Port
Summary: Too right you have!
Message-ID: <375@marvin.moncam.co.uk>
Date: 23 Jan 90 18:34:03 GMT
References: <25B62374.8137@maccs.dcss.mcmaster.ca>
Organization: Monotype ADG, Cambridge, UK
Lines: 32

In article <25B62374.8137@maccs.dcss.mcmaster.ca>, cs4g6aw@maccs.dcss.mcmaster.ca (Amos Yung) writes:
> Hi, folks!
> 
> I am running into trouble again (What else is new?). For some bone-head
> reasons, I have to connect a bone-head device that do not output standard
> RS-232C signal to the serial port. Moreover, I want the output signal to
> trigger a software interrupt. The unfortunate thing is: I really don't
> know much about serial port, RS232C, UART.... kinda stuff. 
> 
Without more info it's difficult to tell exactly what your problem is.
What kind of output have you got available, what kind of signal does it
produce?
FYI : RS232c signals are typically +-12volts relative to ground, though
the spec allows between +-3V and +-24V. Maxell (amongst others) make a
very useful chip, the MAX232 which runs on +5v only, and converts the
normal TTL (0-5V) signals used by your PC to/from RS232 level. The
alternative, if you have +-12 available is a MC1488, if you don't
need to receive from the PC. Don't expect reliable results from a
single rail signal. 
There are lots of UARTS around, but most are micro-controlled, so look
for one which can stand-alone. The IM6402IPL can easily be wired to
send a preset byte whenever the TBRL pin is waggled, or you may be
able to embed some useful info into the transmitted byte. Either way,
you can generate an interrupt at the PC. I suggest the 6402, because
you can hardwire its pins for baudrate/parity/stop bits, it doesn't
need a micro to 'set it up'.
All these chips are cheap, common, and well documented. You should
be able to get data sheets and parts anywhere in the civilised(?)
world.
That should be enough to get you started.

Dave E.