Re: Repairing a SFD-1001 (8250/LP, 8050, 4040, 3040, 2040)

From: Jim Brain <brain_at_jbrain.com>
Date: Wed, 10 Aug 2011 22:47:04 -0500
Message-ID: <4E4350B8.9080905@jbrain.com>
On 8/10/2011 3:10 PM, Hoffmann-Vetter, Martin wrote:
> Hello,
>
>> I don't know how relevant it is to CBM floppy drives, but it seems to
>> have something to do with chip select lines?
> That's one problem when you change an 2332 (rom) to a 2532 or 2732 (eprom).
> The 23xx series has many chip select (cs) signals that can be programmed in
> the polarity. So the standard 2332 for the PET is non inverted chip select
> (cs1) at pin 21 and inverted chip select (cs2) at pin 20. You have the same
> problem with some dos roms eg. 901887-01 and 901888-01. That's a 2364 with
> one non inverted chip select at pin 20!
>
> Back to the 2332. This rom has two chip select inputs. The 2532 has only
> ohne chip select input. The 2732 has one chip select and one output enable
> input. So the 2732 is a better replacement for the 2332. It's used on the
> adapter boards for the sfd 1001 and the 8250lp by commodore.
>
I spent this evening trying to augment my 2364 design to handle 2332 and 
2364, including 2364 with positive CS.  Comments are appreciated:

Schematic: http://postimage.org/image/2n6tytt8k/

PCB: http://postimage.org/image/2n75jl8p0/

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Received on 2011-08-11 04:00:17

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