Date   : Thu, 02 Jan 1986 16:38:40 GMT
From   : john chapman <jchapman%watcgl.uucp@BRL.ARPA>
Subject: Re: Help needed with 8251 USART

> Does anyone out there have any experiece programming the 8251 USART?  I
> am using a Royal Alphatronic PC with CP/M 2.2, and want to be able to
> set and change the baud rate.  I have the data sheets for the 8251, and 
> through much experimentation, I am able to change the baudrate to suit
> my needs.  Unfortunatly, as soon as I try to send data out the port,
> the chip locks up.  Data coming in works fine.  Anyone know anything
> about this?  I can send you the code that I am using if you think
> that you can help me out...
> 
>                                Thanks...
>                                 Mike Spitzer
>                                 mjs@purdue-ecn
>                                 [decvax,ucbvax,ihnp4,inuxc]!pur-ee!mjs

I have tried to do the same thing on two different machines (one multibus
z80 based and the other an s100 8086 based) and found the same thing you
did.  What seemed to work was sending the initialization sequence twice,
e.g. write a subroutine to set up the 8251 and just call it twice in a
row. I'd be interested to know if this works for you......

-- 

       John Chapman
       ...!watmath!watcgl!jchapman

       Disclaimer : These are not the opinions of anyone but me
                    and they may not even be mine.