8251 troubles

[Allison]

>
>Subject: RE: 8251 troubles
>   From: "Chuck Guzis" <cclist at sydex.com>
>   Date: Sun, 27 Apr 2008 11:12:06 -0700
>     To: cctalk at classiccmp.org
>
>Date: Sun, 27 Apr 2008 08:23:09 -0700
>From: dwight elvey <dkelvey at hotmail.com>
>
>I'm going to assume that you have an 8251A, not an 8251.  If the 
>latter, either sell it to a collector or have it bronzed and made 
>into a tieclasp.  There are substantial differences between the -A 
>and non-A parts, all annoying.

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.

>The implication is that since the command register's write-only, you 
>have to remember the last command you sent if you want to reset the 
>error flag.  One of the minor annoyances of a few early Intel 
>peripherals.

Yep, helps to have a table of set up variables.

>Anent that last one--make certain that your handshake lines 
>(RTS/CTS/DTR) are set to the proper levels--an inactive CTS will 
>prevent the 8251A from transmitting.

Yep,

Allison