CRC question

Chuck Guzis cclist at sydex.com
Sat Nov 10 15:51:02 CST 2007


On 10 Nov 2007 at 15:24, Roy J. Tellason wrote:

> Just lookingat the picture in that file I retrieved makes me want to play with 
> that thing a bit.   :-)   I think,  though,  that instead of the 2 5.25" 
> drives I was originally intending to use with it (and which are buried 
> somewhere in storage at this point,  I have no idea where),  I'd like to 
> maybe have a go at interfacing a 3.5" drive to it.  And maybe one of 
> the "smaller" (2G?) SCSI drives I have around here.  Think that's possible?

Certainly the SCSI drive is possible, given the interface on the BBII 
(Doesn't have a SASI-ready interface or two already?)  Not wide-SCSI, 
but certainly 8-bit SCSI.  Your biggest problem is how to deal with 
2GB efficiently with CP/M-80.

3.5" floppy is easy, but a 3.5" PATA drive is more problematical, 
given the 16-bit interface for data.  Of course, one could throw away 
half the data or even treat the drive as two units to accommodate 8-
bit transfers.

>Best I can remember,  the code did a bunch of 16-bit math that 
>seemed to implement some kind of a polynomial (just a bit beyond me 
>when I read it) and ran this over the contents of the EPROM,  
>looking for a zero result. 

Could even be XORing the contents with a LFSR.  Hard to say without 
seeing it. 

Cheers,
Chuck




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