Customizing KEYSCAN routine (my own keyboard)

[MIRKOSOFT]

Hi!


I tried to customize KEYSCAN routine for my own Slovak keyboard.
So, I redirected vector at $033c to my own routine and test only one key (other yet inactive), but always when I press a key it jumps to ML monitor as error and PC shows illogical address which has nothing with my routine. Where I'm doing it wrong?
Here's bit of code:

Code Select Expand


.var toscreen = $ffd2
.var rvs = $f3

.pc=$2000 "Charset"
.import c64 "sk-font.bin"

.pc=$2800 "SK-activator"      // $2800 = #10240

   lda #$15
   ldx #$28
   sta $033c
   stx $033d
   rts

.pc=$2815 "SK-driver"

slovak:
   cpx #00
   beq ok
   jmp original_scan
ok:   stx csflag
   pha
!loop:
   cmp #$31      // 1
   bne !+
   jsr key1
   jmp endofscan
!:   cmp #$32      // 2
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$33      // 3
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$34      // 4
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$35      // 5
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$36      // 6
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$37      // 7
   bne !+
   jsr donothing
   jmp endofscan
!:   cmp #$38      // 8
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$39      // 9
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$30      // 0
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$2b      // +
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$2d      // -
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$5c      // Ł
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$3d      // =
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$5a      // Z
   bne !+
   jsr donothing
   jmp original_scan
!:   cmp #$59      // Y
   bne original_scan
   jsr donothing
   jmp original_scan
original_scan:
   jmp $c6ad
donothing:
   rts
endofscan:
   lda #29
   jsr toscreen
   ldx csflag
   pla
   jmp $c6c4
   
csflag:
.byte 0

line:
.byte 0

column:
.byte 0





Many thanks for every help.


Miro

[Hydrophilic]

First problem is you are corrupting the stack when you get an unknown key.  At start of routine ('ok') you issue PHA but this is only fixed by PLA if a known key is pressed ('endofscan').  When other key is pressed, it exits via 'original_scan', but it does not PLA.  So stack is corrupt and eventually CPU goes to wrong location (via RTS or RTI).

A second minor problem is with the name, vector $33C is for KEYCHK not KEYSCAN.  This caused me confusion at first!  The vector is taken, if a key is pressed, sometime during Editor routine SCNKEY ($C012: JMP $C55D).