Re: Rev. C SCSI v2 from GSE-Reactive.com

["Henry" <apl2research(at)comcast.net>]

Another quick update.

Found out my SCSI HDD is fine.  I fried the terminator.  Now I need to find 
a 50 pin external terminator.  Luckily I had some term packs I was able to 
install in the drive.  At least it's working again.

My old Rev. C card works but the new one just crashes in to monitor on boot. 
:-(  Now the fun part - checking all the I/O lines of the CPLD to the 
schematic.  Would be nice if it was that simple, but I'm not holding my 
breath.  I knew what the risks were trying to incorporate an incompatible 
design in a CPLD.  We tried to do what made the most sense to make it work 
though.  Normally one would start small and remove logic in steps, not try 
to 'stuff' the entire board in the first shot.  It was worth a try though. 
The main thing is we learned so much by doing what we did.

We'll waste a little more time with it then call it a day.  We have to many 
other things to worry about right now and there's not too much more to be 
learned from this project.  Our efforts could be spent working on other CPLD 
projects and continue our learning while making progress.  If there are any 
other results I'll post them here.  There are three boards that could be 
sent out if anyone want's to take a look at how it's crashing and make some 
suggestions as to what it may be.  Just email and ask.


-- 
Henry S. Courbis
www.GSE-Reactive.com
Apple II Series Legacy Hardware - Come take a look at what we have to offer!

"Henry" <apl2research(at)comcast.net> wrote in message 
ceCdnVzIqrOqLqjZnZ2dnUVZ_vOdnZ2d@comcast.com">news:ceCdnVzIqrOqLqjZnZ2dnUVZ_vOdnZ2d@comcast.com...
> Hello everyone.
>
> Just a quick update on the Rev. C SCSI CPLD project.  I know a few of you 
> have been curious as to how this project is coming.
>
> Here's a link to my Web Server with some pics:
> http://reactivecomputers.gotdns.com/Rev.%20C%20SCSI/Rev.%20C%20SCSI%20v2/
>
> The card is built.  The CPLD has been programmed.  I connect it to my 
> external SCSI Hard Drive... and then notice the Hard Drive is dead.  What 
> a disappointment!  It was working last week.  I had setup and formatted a 
> 32 Meg volume with a Rev. C SCSI card and was going to use it as a test 
> volume for the Rev. C SCSI v2 prototype.  Oh well.  So much for plans.
>
> Any one have a SCSI Hard Drive they would be wiling to sell me so I can 
> replace the one in my external enclosure?  Doesn't need to be large, just 
> working.
>
> If you look at the pictures you'll notice the CPLD's pins are quite small. 
> .5 pitch actually.  About three will fit in the width of the edge of a 
> dime! Not fun soldering but I finally got the hang of it.  I don't hold 
> much hope the prototype will work though.  Apple's design does work, but 
> is really quite messy.  Signals 'feed' back in to places they shouldn't 
> (to save PCB space and chips I guess) and coming up with code to emulate 
> their design was really quite hard, if not impossible.  You may notice 
> some small logic IC's still on the board.  The main reason for them is 
> that they convert a 'week' 1 or 0 (high or low) single to a true single. 
> You can't write a piece of code for a CPLD that says "if the voltage is 
> 1.6 volts drop it to 0 volts or if it's 2.8 volts make it 5 volts".  Or I 
> should say it can't be done in code and cheaper and in less parts then the 
> original logic chip.  Since there won't be much demand for the Rev. C 
> compared to the HS SCSI or RAMFast controllers completing a working model 
> isn't a high priority.  We've learned a lot when it came to this project 
> and that knowledge will be invaluable in future projects.  Next time a lot 
> more time will be spent 'cleaning up' the actual design before any CPLD 
> work would begin.  Not all issues can be over come by code.  We also 
> learned that the Altera software is much easier then the Xilinx software 
> and tends to lend itself to converting the older 'through hole' designs 
> better.  The next projects will probably use an Altera chip.
>
> Just taking a break.  Back to my taxes. :-(
>
>
> -- 
> Henry S. Courbis
> www.GSE-Reactive.com
> Apple II Series Legacy Hardware - Come take a look at what we have to 
> offer!
>
>