Caple C871i Manual de usuario descargar pdf (Pagina 264)

100

101

Apple II Computer Info

near the ROM socket using epoxy.

o- 74LS04 pin 14 goes to ROM socket pin 24

o- 74LS04 pin 7 goes to ROM socket pin 12

o- any trace to ROM socket pin 21 would be cut and

ROM socket pin 21 would be jumpered to ROM socket pin 24

o- any trace to ROM socket pin 18 would be cut and

ROM socket pin 18 would be connected to 74LS04 pin 2

o- pin 1 of the 74LS04 goes to the trace which used to go to ROM socket pin 18

After these mods, the PROM would be swapped in for the ROM.

Let me know if you see any screw-ups in the above.

Our setup is different because we did several mods early (before getting a

Language Card) and ended up with the PROM on the main board with an option to

switch

to the ROM on the LC.

The reason for being able to swap in the regular ROM is that we made many

changes to the $F8 ROM code and wanted to get around ROM checks which a few old

copy

protected programs do upon booting. (I don't know if the minor mod to enable lower

case input will get past all such ROM checks-- it certainly would not pass a check

sum test.) Anyway, the checks are fairly rare.

Hmmm-- what about this code substituttion instead of just NOPing everything:

FD7E- C9 C0

FD80- 90 02

FD82- 29 FF

It diddles things around so that the checksum is right and the AND #$FF

leaves

the input alone whatever the branch at $FD80 decides. (According to the ROM code

listing, there are no branches which go into the middle of this code and flags

status doesn't matter because the code quickly does another compare operation

after

saving the input.)

Rubywand

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Apple II Computer Technical Information : Apple II Family Hardware Info

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Caple C871i Manual de usuario Pagina 264

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Caple C871i Manual de usuario Pagina 264

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