[Coco] 16550 wasRe: RS232 paks

[Gene Heskett]

On Wednesday 04 March 2009, Mike Pepe wrote:
>Roger,
>
>The 6551 does have a nasty bug where a state change in the hardware flow
>control causes partially transmitted (or assembled?) characters to be
>dropped.
>
>I would guess that in what you're doing, things are totally software
>driven and in tight loops where such conditions would not happen.
>
>In a multitasking environment such as OS9 what Mark says is much more
>applicable. I'd agree in that situation I'd take a 16550 over a 6551 any
>day.
>
>
>
>-----Original Message-----
>From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com]
>On Behalf Of Roger Taylor
>Sent: Wednesday, March 04, 2009 11:40 AM
>To: CoCoList for Color Computer Enthusiasts
>Subject: Re: [Coco] 16550 wasRe: RS232 paks
>
>At 09:40 AM 3/4/2009, you wrote:
>>Willard,
>>
>>The NitrOS-9/Driver is already written for a 16550 device. I have
>>had a homebrew card running for almost 10yrs based upon that chipset.
>>
>>Yes, it would break all the old term programs. A caveat of adding
>>new technology to an old machine. Not a problem in NitrOS-9 as the
>>driver/dd is not part of the actual program, when properly written.
>>
>>The SuperBoard has a multi-function chip on it that has the 16550 in
>>it. Anyone that has done high speed serial testing in a system will
>>design it with hardware handshaking. It is no secret that the
>>ACIA(6551) has issues with this, plus almost no buffer space. Not a
>>good choice for new designs, IMHO. 16xxx series offers GREAT
>>buffers, programmable interrupt thresholds etc..... I guess that is
>>why they are so common, oh they work too! :)
>>
>>Regards,
>>
>>Mark
>>Cloud-9
>
>Mark,
>
>Exactly what problems have you yourself had with the 6551 so that I
>may try to offer a software solution?  I'm not claiming to have all
>the answers, but I've done a serious amount of 6551 coding in the
>past, and I can assure you that the chip itself is not always the
>problem.  The programmer is 90% of the problem.  The OS is 90% of the
>problem.  If there's some little bug or dislike about a certain chip,
>I guarantee that there's the same number or more in the 16550.  I've
>read about that chip and based on how many variants are floating
>around, how can anyone ever agree on a right way to code the
>routines?  It appears to be a mess, no less than what you claim about
>the 6551.  I'm not saying any certain chip is BETTER than the other..
>I'm saying that TOO many programmers and nonprogrammers have clashed
>about these chips and in the end, they're all still being used
>today.  You can always tell when the programmer took shortcuts or
>just didn't know what he was doing.
>
>When you say the 6551 is not a wise choice for any new designs, your
>intent is clear but the statement is not true.  Someone who's put out
>a new wireless RS-232 pak didn't just wake up yesterday and discover
>the 6551.  People who know how to write good software aren't afraid
>of the 6551.
>
With sockmasters fix it does the 7 wire hardware protocol flawlessly.  I didd 
at one time using it between the coco and an amiga, this while I was doing the 
last version of zmodem, (rzsz-3.36.lzh?), and there I never had a problem even 
when the tally lights on an rs232 sniffer were indicating flow was disabled 
1/4/th of the time while using 9600 baud and getting 730cps.  I have also used 
it to move files to/from the coco using minicom on this box although without 
visible rs232 flow tally leds.

>My wireless RS-232 pak has been connected to 7 CoCo units (2 CoCo
>1's, 1 CoCo 3, 4 CoCo 2's) and to 2 PCs @ 115200 bps running lengthy
>looping tests (1-2 days sometimes), and I haven't seen it bomb out
>yet.  Can you please tell me what circumstances I need in order to
>break my protocol ?

I haven't found a ush<->bluetooth gismo yet Roger but I'm still looking, I 
need to get rid of the direct wire as mother nature has blown some usb 
extension cabling already, and I can't think of a better way to get good 
isolation than this pack of yours.


-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Beware of geeks bearing graft.