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From: rainer@boulder.Colorado.EDU (Rainer Malzbender)
Newsgroups: sci.electronics
Subject: Re: UARTs, uControllers, & Serial Data
Message-ID: <24897@boulder.Colorado.EDU>
Date: 18 Aug 90 22:29:51 GMT
References: <21000091@m.cs.uiuc.edu>
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Reply-To: rainer@boulder.Colorado.EDU (Rainer Malzbender)
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In article <21000091@m.cs.uiuc.edu> totty@m.cs.uiuc.edu writes:
>
> .. stuff deleted ..
>
>	(1) What simple UARTs to people recommend, especially simple ones
>	    whose options can be hard-wired and not require writing words
>	    or initialization data to the UARTs?

Back in the bad old days I used to use the AY-5-1015 uart. Everything is
programmed using dedicated pins on the chip. I think Jameco and JDR still
sell this dino. See below.

>	(2) Are there any chips to do what I want (synchronous serial to
>	    RS-232)?

My favorite uart is the Signetics 2681 dual uart. Unfortunately it is only
asynchronous. However, its cousin, the 2661, does both sync and async. So
does the Intel 8251A (I have an old databook, there may be newer versions).
Both will require a micro unless you are really twisted.  See below.

>	(3) Would it make sense to use a microcontroller instead?  If so
>	    what microcontrollers are recommended, how wide are their I/O
>	    paths, and what support circuitry do they need?  Are they
>	    easily programmable?
>

Let's face it, micros win most of the time, as much as the dyed-in-the-wool
hardware types protest. Get a 68HC11, 8031, or something like those. Having
done a similar thing with an 8031 I can tell you that it takes exactly one
eprom and some TTL-to-RS232 level converters (a single MAX232 with caps or
1488/1489 combination) [1].  Use one of the general purpose I/O bits to sample
the sync input, and send what you get out the built-in uart. The built-in
timer gives you a sample clock (assuming you're not running too fast). For
this application even the 128 or 256 bytes of internal RAM (depending on
which specific chip of the 8031 family you use) would be sufficient. The
August '88 Byte has an intro article on the 8031. Both are 8 bit micros,
and public domain assemblers exist for them. If you pay money you can get
nice C compilers with emulators and debuggers, but for this application
you can almost hand assemble the code anyway. 

[1]: Forgot, there's a latch involved also. Ok, eprom, latch, micro, and
MAX232.

--
Rainer M. Malzbender                          Technology recapitulates biology.
Dept. of Physics                (303)492-6829       rainer@hibachi.colorado.edu 
U. of Colorado, Boulder, USA                  malzbender%opus@vaxf.colorado.edu