Newsgroups: comp.robotics
Path: brunix!uunet!stanford.edu!ames!elroy.jpl.nasa.gov!forsight!gat
From: gat@forsight.jpl.nasa.gov (Erann Gat)
Subject: Re: Miniboard 2.0 & NMI F68HC11
Message-ID: <1992Aug28.163912.7108@elroy.jpl.nasa.gov>
Keywords: Miniboard
Sender: news@elroy.jpl.nasa.gov (Usenet)
Nntp-Posting-Host: robotics.jpl.nasa.gov
Organization: Jet Propulsion Laboratory
References: <1992Aug27.142429.16553@hubcap.clemson.edu> <1992Aug27.205711.23050@news.media.mit.edu> <1992Aug28.135419.3725@hubcap.clemson.edu>
Date: Fri, 28 Aug 1992 16:39:12 GMT
Lines: 29

In article <1992Aug28.135419.3725@hubcap.clemson.edu> dawill@hubcap.clemson.edu (david williams) writes:

[Talking about the Maxim MAX233 RS232 level converter chip]

>   As a matter of fact, I've used this critter before, and it works
>very well.  I can't say enough about Maxim's products:  they do what 
>they're supposted to, first time.

I have an interesting testimonial to the MAX233.  I used one to connect
a New Micros 6811 board to my Macintosh.  I had been using it for several
months and it worked like a charm.  Then one day I decided to make a
second MAX233 board, so I traced out the wiring on my original (since
I had lost my schematic).  To my amazement I found that the chip's Vcc
pin was disconnected.  Not just a broken connection; there was no wire
there at all.  The thing had been working beautifully for months
WITHOUT POWER!  I doff my hat to the Maxim designers.

BTW: Re the discussion of whether there should have been a MAX233 on
the miniboard: I think it makes more sense to build a separate little
board with a MAX233 on it.  Consider: there are two ways in which the
6811 asynchronous serial port can be used, to talk to a terminal or
to talk to other 6811's.  When 6811's talk to each other they usually
don't need to level-shift, and presumably one only uses one terminal
at a time.  A Max233 chip consumes quite a bit of real estate (on the
scale of the miniboard, anyway).  I think it's a defensible design.

Erann Gat
gat@robotics.jpl.nasa.gov

