Patch Commodore 64 Kernal Roms to remap keyboard

Punctuation remapped Commodore 64 keyboard layout

I have presented software and drivers to remap the Commodore 64 keyboard before.  But those solutions install into lower BASIC RAM at a fixed location, and disappear when you restart your computer.

Because the KERNAL ROM stores the keyboard mappings (4 maps: Normal, Shift, Commodore, and Control), if you can replace the ROM, you can remap the keyboard.

Here I present a new program of mine: 64KEY ROM PATCH (PRG) added to c-keymaps project.

This program will find where the keyboard mappings are, and with a patch list (DATA statements) containing shift mask, key scan code, and PETSCII character, will patch the ROM into RAM with changes and activate the ROM.

From here, you have some choices.  You can use the program on demand as is, or make the change more permanent.

For those with physical machines, there are already processes for replacing your ROMs.  You can search for them.  Now that the ROM is in RAM, you can figure out how to save to a file, transfer to your PC, and flash a ROM replacement to insert into your C64.   This change is semi-permanent in that the keyboard mapping will be there as long as the new ROM (usually EEPROM) is in place.

If you have a ROM switcher capability (Easy Flash 3), or a toggle switch allowing physical switching between multiple ROMs (may be piggy backed with a toggled chip select), then you change on the fly.

And if you run an emulator, you can save the patched ROM into your collection of C64 ROMs and choose it as your current ROM.

The BASIC program includes the following maps (effect is shown in the screenshot above):

300 rem patch table
310 rem shift,scancode,petscii
320 data 0,40,45:rem + to -
330 data 0,43,61:rem - to =
340 data 0,46,91:rem @ to [
350 data 0,49,93:rem * to ]
360 data 0,54,92:rem ^ to \
370 data 0,45,59:rem : to ;
380 data 0,50,39:rem ; to '
390 data 0,53,13:rem = to return
391 :
392 data 1,59,64:rem " to @
393 data 1,19,94:rem & to ^
394 data 1,24,38:rem ' to &
395 data 1,27,42:rem ( to *
396 data 1,32,40:rem ) to (
397 data 1,35,41:rem shift 0 to )
398 data 1,40,95:rem shift + to l.arrow
399 data 1,43,43:rem shift - to +
400 data 1,53,141:rem shift = to s.ret
401 data 1,45,58:rem shift : to :
402 data 1,50,34:rem shift ; to "
408 data 1,57,221:rem shift _ to v.bar
409 data 2,57,219:rem cbm _ to cross