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'[PICLIST] [OT] Website? UART?'
|>I don't think so, remember they didn't have fifos, internal baudrate
>gens etc. in those days... All you need is a shiftreg, some clock
>dividers and a pretty simple state machine - rather less than even a
>4004. I'm sure you could do it with less than a dozen 74TTLs
>There was also a Texas Instruments chip that was pin compatible to these.
>a problem operating at high speed (as in 9600B was high speed) and would lock
>up. The system we had these in was connected to a Burroughs machine which ran a
>polled network, so in went a timer that reset the chip if there were no polls
>received over a certain period.... Then we got some 6402 chips and the problem
>was solved properly.
Well, I did build my own UART and it took about 10 TTL chips. It
had a bug, too, because I jumped from the parity bit to the stop
bit without waiting. The state machine was just a counter. The
baud rate was done with a 555 and a 10-turn pot. It was NOT
stable but I could "tune" it each time until it worked.
I had seen these all-in-one chips called "UART"s at swap meets
but they were rare and I didn't get to the swap meets all that
often. Finally I decided to get one (like $6) and so made
myself a pc board and assembled the thing. It worked, too.
Until one day I got +5 across one of the outputs and then,
no more chip! I was sunk. I'd ruined my board. Lo and
behold, a friend got me some datasheets for this chip and we
discovered, as Alan said, that it (the TI 6011) was indeed
pin-for-pin compatible to the AY-5-1013. I was saved!
I still have all that stuff. One day I'll get a digital
http://www.piclist.com hint: The PICList is archived three different
ways. See http://www.piclist.com/#archives for details.
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