LZ: Re: Problems with the attached file and other comments.

Subject: LZ: Re: Problems with the attached file and other comments.
From: Mel Tsai <tsaimelv@pilot.msu.edu>
Date: Wed, 11 Sep 1996 18:36:02 GMT
In-Reply-To: <Pine.SV4.3.93.960911141130.26178B-100000@gopher.chem.wayne.edu>

On Wed, 11 Sep 1996 14:24:03 -0400 (EDT), "Jonathan F. Freeson"
<jfreeson@gopher.chem.wayne.edu> wrote:

>Mel: As for comments on your circuit, as for your circuit, It looks =
good.
>I didn't get a chance to go through it in detail but I like it.  One =
thing
>I would add however is some support for a checksum of some type.  For =
one
>thing, I know that PC cable I made to connect from my TI to my PC is a
>little touchy at times  (Although I could have done a better job making
>it, but I didn't really care).  I would use a simple parity checksum on
>the entire (what I belive to be) 24 send bits and a similar one on the
>receive bits? =20

I thought about this, but I figured it would be easier to do it the
way the TI-85 does it.  When you send a file to the expander, you send
a checksum byte to it (and then read it back to make sure there were
no errors in the checksum byte).  Then, when you want to reload the
file back to the TI-85, compare the checksum of the file with the
checksum byte, and if there was a difference you should read it again.
Of course, the file itself may have been corrupted during
transmission, so the parity checker may be necessary!  Anyone have any
suggestions to do a hardware parity check?

>Now that I think about it, a toggle flip-flop might do the
>trick. =20
>

What exactly do you mean by this?

>Another comment:  The power requirements for the board should not be =
much.
>I have powered a 68HC11 circuit w/ various IC's with a 9V battery and a
>voltage regulator. I'd say try it with a 9V Battery. =20
>

Remember, though, the 68HC11 is a new generation of extremely low
power microcontrollers, so the power requirement may be a bit
different.  However, it will probably work on a 9V battery, but it may
not have extremely long battery life (as compared to using AA's or
AAA's.).

-Mel

References:

From: