This brings seeral questions about the hardware.
What is the state of CTS/ (clear to send active low) if the state of
the input is false it will never send. It effectively disables the
transmitter and can be used for hardware handshake.
Also the command instruction must have bits 0 and 2 set to enable Tx
and RX repectively. Typical command byte would be 35H or 37H.
>Subject: 8251 troubles
> From: dwight elvey <dkelvey at hotmail.com>
> Date: Sun, 27 Apr 2008 08:23:09 -0700
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
> I've got a funny problem with a 8251.
> I've been writing 8080 code and seem to have a strange
> I initialize the chip in async mode. I have a light box on the
>serial wire. It is initialized to both send and recieve.
> I send one character to the 8251 and it passes it to the software
>on the 8080 side. I display it on the 8080 side.
> I then send another character to the 8251. Nothing happens.
>It won't receive until I reset it.
> None of the status lights change. I can see the data light flicker.
> It could be a bad part but it just doesn't seem that it would
>work once and then fail to work for the second character.
> It just doesn't make sense.
> Is there something I'm missing about the 8251.
>Spell a grand slam in this game where word skill meets World Series. Get in the game.
Are you really looking for sony floppy drive model#MP-F52W-00D ,
Please be informed that I do have 2 unit of the above item.
I am looking for a Sony floppy drive Model# MP-F52W-00D. Do you have any
information on how I could obtain one? Please reply to both e-mail addresses
in this message.
For nearly five years I have had some pages on my website
regarding the MicroProfessor MPF-1. These pages included
binary images from the ROMs and redrawn schematics along
with other technical information. This was done with the
understanding that I had a tacit agreement from Flite
Electronics to so do having discussed these pages with a
representative of Flite.
Now I have received what can only be described as a thinly
veiled threat from one of the directors of Flite demanding
certain actions on my part but not, strangely, the removal
of any of the disputed information.
What I would like is some help on what I can freely publish
without having to worry about any action from Flite.
As Flite and I are both in the UK this at least does not
include the problems of crossing any legal borders.
And, just in case any Flite directors read this list, when
you prefix the question "Indeed, I am being very polite and
conciliatory?" with the threat of "?causation and damages?
through your public domain exposure of our copyright
material for so long." then no, you are not.
>Subject: RE: 8251 troubles
> From: "Chuck Guzis" <cclist at sydex.com>
> Date: Mon, 28 Apr 2008 11:22:58 -0700
> To: cctalk at classiccmp.org
>> Date: Sun, 27 Apr 2008 15:41:49 -0400
>> From: Allison
>> I have both in quantity. Generally it's the quirks of the
>> "improved part"that are annoying but for simple Async serial IO
>> they are identical enough.
>It could be that simple polled-mode async I/O works well enough, but
>when I was trying to get a bisync package working with the 8251, I
>wanted to chew my own arm off. Among the issues (other than the
>occasional device "hang") that I had was the lack of double-buffering
>and the indeterminate control logic (it was possible to disable the
>transmitter in the middle of a character). The 8251A was *much*
>better in that respect.
For async its ok bisync, you gotta be crazy. While the A helped
bisync it broke the CTS/ CTS to inactive during a TX meant the
character would be resent! The Fix was for both A and non A
is a gate to interlock the external CTS/ with TXE.
>In any case, Dwight has the NEC part which renders the topic moot.
Not really as it had the exact same bugs.
>I found at the time that the Signetics 2651 was a far better chip for
>most utility purposes than the 8251, having the benefit of an
>internal baud-rate generator for async operation.
It was better.
> Date: Sun, 27 Apr 2008 15:41:49 -0400
> From: Allison
> I have both in quantity. Generally it's the quirks of the
> "improved part"that are annoying but for simple Async serial IO
> they are identical enough.
It could be that simple polled-mode async I/O works well enough, but
when I was trying to get a bisync package working with the 8251, I
wanted to chew my own arm off. Among the issues (other than the
occasional device "hang") that I had was the lack of double-buffering
and the indeterminate control logic (it was possible to disable the
transmitter in the middle of a character). The 8251A was *much*
better in that respect.
In any case, Dwight has the NEC part which renders the topic moot.
I found at the time that the Signetics 2651 was a far better chip for
most utility purposes than the 8251, having the benefit of an
internal baud-rate generator for async operation.
>> This was done with the understanding that I had a tacit
>> agreement from Flite Electronics to so do having
>> discussed these pages with a representative of Flite.
> Do you have any of this in writing (or email)?
I may have. This was nearly five years ago and I'm hoping
that the emails from Flite are among those I have archived.
> The information seems to be gone (or I'm looking in the
> wrong place).
As it was the easiest option it has gone for now at least.
>> What I would like is some help on what I can freely publish
>> without having to worry about any action from Flite.
> Presumably nothing of theirs.
That's what I need to sort out. Can I post a redrawn schematic?
How about board pinouts, or system descriptions?
> uk.legal might be the place to start.
It may indeed, thank you.
I'm doing a bit of spring cleaning so I have a Sharp Hayac 2900 with disc's
and manual looking for a new home.
I like to trade it for HP stuff (printers HP-1000 interface or computers
I also have a MicroVax II for trade (this a BA23) with cpu 2Mb memory and
disc and TK-50 controllers but no disc or tape drive.
If you don't have any of this well maybe we can work someting else out.
I live in the Netherlands.