Xref: utzoo comp.dcom.modems:7474 sci.electronics:15825
Path: utzoo!attcan!uunet!ogicse!zephyr.ens.tek.com!gvgpsa!gold.gvg.tek.com!grege
From: grege@gold.gvg.tek.com (Greg Ebert)
Newsgroups: comp.dcom.modems,sci.electronics
Subject: Re: UARTS for speed...
Keywords: UARTS, 8250, 16450, 16550A
Message-ID: <1693@gold.gvg.tek.com>
Date: 21 Nov 90 18:29:39 GMT
References: <1990Nov21.145421.23315@elroy.jpl.nasa.gov>
Followup-To: comp.dcom.modems
Organization: Grass Valley Group, Grass Valley, CA  95945
Lines: 31


 cyamamot@kilroy.jpl.nasa.gov (Cliff Yamamoto) writes:
> [...]
>Can anyone tell me if the 8250, the 16450 and the 16550A are pin-for-pin
>interchangable?  I'm not sure if I have the 8250 or the 16450, but I'd like
>to eventually plug in a 16550A.  Also do all three share the same port and
>programming characteristics?  Are 16550A readily available?
>

The 8250 and 16450 are pin interchangeable, and the 16450 is an 'enhanced'
version of the 8250. I dunno what the enhancements are.

The 16550 is *NOT* pin compatible (but quite close). It is upward-compatible
from a software viewpoint from the 16450; you have to enable the FIFO mode.
If you want to install a 16550, you need to rework pins 24 (CSOUT on 16450,
TXRDY on 16550) and 29 (NC on 16450, RXRDY on 16550). These pins show FIFO
status.

You can get all 3 from Jameco.

A comment on the 16550: It's a *NEAT* chip. The FIFOs really cut down on
interrupt overhead, especially at high data rates.


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