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
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
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.