Re: Someone the contents of DISK II FSM ROM P6A (TBP28L22)

[josephoswaldgg@hotmail.com (Joseph Oswald)]

russotto@grace.speakeasy.net (Matthew Russotto) wrote in message news:<HO-dnYfTc9itgLndXTWc-g@speakeasy.net>...
> In article <6257c13b.0402061014.77cd0f2c@posting.google.com>,
> hanshein@web.de <hanshein@web.de> wrote:
> >
> >Does someone have the contents of the PROM? I 
> >obtained the PROM datasheet from www.ti.com 
> >naming the pins of the PROM....
> >
> >However, I would prefer not to replace the PROM
> >on my DISK II card and build a interface to read
> >it out if someone already did it.... 
> 
> Aren't P5 and P6 the same PROM type?  If so, assuming you have an
> Apple, just put P6 in P5's slot, disconnect the drives, and read the
> 256 bytes from Cx00 in the monitor.

Yes, P5 and P6 are the same PROM type. However, the address lines and
data lines are arranged differently. Since you have the schematic, it
is possible to trace out the differences.

The swapping of P5/P6 is a classic trick, which I saw in Sather's
"Understanding the Apple II." Ideally, you have a tape cassette player
to save the P6 ROM contents without the disk drive.

Or, you can find a copy of "Beneath Apple ProDOS" or "Beneath Apple
DOS." They have a listing of the sequencer. The presentation of the
write-protect sense is wrong in one detail (they indicate that the WP
state gets loaded into all bits instead of  shifted in from the MSB),
they give short shrift to the read pulse latching circuit, and they
almost totally ignore the write sequence, but it is 90% of what you
need.

I once found a P6 ROM listing through Google, but you have to be
clever with the search terms, and I can't seem to remember the trick.