Pinout for SED9421

[Dwight K. Elvey]

>From: "Allison" <ajp166 at bellatlantic.net>
>
>>
>>Subject: Re: Pinout for SED9421
>>   From: "Dwight K. Elvey" <dwight.elvey at amd.com>
>>   Date: Mon, 28 Nov 2005 10:46:28 -0800 (PST)
>>     To: cctalk at classiccmp.org
>>
>>>From: "Allison" <ajp166 at bellatlantic.net>
>>
>>>>   From: woodelf <bfranchuk at jetnet.ab.ca>
>>---snip---
>>>
>>>>Did anybody ever use a serial chip and a data separater
>>>>rather than a floppy disk controler?
>>>
>>>Yes, many.  usually its a sync chip.
>>>
>>>Allison
>>
>>Hi
>> Besides the HeathKit hard sectored controller board,
>>used on both the H8 and the H89, Polymorphics also
>>used a serial chip to do data. In both of these
>>cases, as you state, they used synchronous serial
>>chips and not async.
>
>Err, Yes that's what I did say.  Sync chips were the norm

Hi Allison
 I'm not contridicting, just pointing out some cases
to support. As I recall, the N* controller also used
the synchronous serial chip. I don't know of a case
that used a async part. All of these were used on
hard sectored disk.
 I don't know of any soft sectored that used serial
chips. I suspect that it is because these depended
on using illegal data clocking sequences in order
to mark sectors. This would require more external
circuits.
Dwight

>for brewed designs there were not OSI or done with TTL.  
>
>Often they were used because WD could not supply or was
>not viewed as the desireable item due to lack of second 
>source (at least early on).  Some did it to have a 
>propritory format.
>
>
>Allison
>
>
>