Re: EOR 02D6,Y For Disk II Family Again

["Charlie" <charlied@NOSPAMbboard.com>]

"Bryan Parkoff" <BParkoff@satx.rr.com> wrote in message
jv6cnalIvfC_r8GjXTWQlg@giganews.com">news:jv6cnalIvfC_r8GjXTWQlg@giganews.com...
>     I have found that PROM code is clear to me since the Beneath Apple
> ProDOS manual is completely wrong.  Appendix C -- Nibblizing contains
> paragraphs and figures.  I assure that paragraphs are the most correct while
> it explains clearly, but stage 2 and stage 3 in figure C.12 and C.13 are
> completely wrong.  Two last bits each byte should be stripped off in both
> Aux 2 and User 2 before EOR can be used for checksum.  Eighty-six bytes
> should be reversed from $00-$56 to $56-$00.  After stage 2 will be done
> correctly, the translation table for stage 3 will be always correct.
>     I do not understand why writer did not review the figures carefully
> before the book was published for public.  It is now clear to me since I
> have spent couple hours figuring in my own.  I have solved the problem.
>

Bryan,

Although I found the tables in "Beneath Apple ProDOS" to be a little confusing
I don't believe they are wrong.  Those tables show the stages of WRITING to the
disk.  The boot ROM code (at $C600) is for READING from the disk.  The stages
described in Appendix C would naturally have to be reversed for reading.

Charlie