Short program with bugs for hackaday supercon 2022 badge, slot machine

slots.asm

init:		; Steven Smethurst, 2022. Based on Hackaday-dice-roll by Tom Nardi
mov r0, 2	; Set matrix page
mov [0xF0], r0

mov r0, 5 	; Set CPU speed
mov [0xF1], r0

main:
gosub getroll	; Put random number in R1
mov r2, 1	; Subtract 1 from result to get mem address
sub r1, r2
gosub drawdie	; Start drawing routine
ret r0, 0	; Badge will halt on an un-called return, ending program

getroll:	; Get random number between 1 and 6 
mov r0, [0xff]	; Read from PRNG
cp r0, 7	; Check if R0 less than or equal to 9
skip nc, 1	; Skip jump if previous is true
jr -4		; Skip back to PRNG read
cp r0, 0	; Check if R0 equal 0
skip nz, 1	; Skip jump is previous is true
jr -7		; Jump back to PRNG read
mov r1, r0	; Copy R0 to R1
ret r0, 0	; Return from sub

drawdie:
mov pch, 1	; Set high jump coord
mov pcm, r1	; Mid address maps to die face
mov jsr, 0	; Execute jump with lowest nibble, R0 now loaded with 4 bits

mov r7, 0	; Init counter
mov r5, 0	; Set initial row
mov r3, 2	; Set right matrix page
mov r4, 3	; Set left matrix page

mov [r3:r5], r0 ; Draw right-side nibble
inc jsr		; Inc lowest bit reads next nibble
mov [r4:r5], r0	; Draw left-side nibble
inc r7 		; Inc counter
mov r0, r7	; Move counter, can only compare to R0
cp r0, 16	; Check if we've looped 8 times
skip z, 3	; Skip next 3 lines if true 
inc r5		; Move to next row
inc jsr		; Read next nibble
jr -10		; Loop around
ret r0, 0	; Return from sub

; Symbles: Diamond, Heart, 7, X  
; 1 = Diamond, Heart 
; 2 = Diamond, 7 
; 3 = Diamond, X
; 4 = 7, Heart 
; 5 = 7, X 
; 6 = X, X == Winner 
;
; 2


org 0x100
dicegfx:	; Graphics data
; 1
	BYTE    0b10000011 ;  X
    BYTE    0b11000110
    BYTE    0b01101100
    BYTE    0b00111000
    BYTE    0b00111000
    BYTE    0b01101100
    BYTE    0b11000110
    BYTE    0b10000011
    BYTE	0b00011100 ; Heart 
    BYTE	0b00111110
    BYTE	0b01111000
    BYTE	0b11110000 
    BYTE	0b11110000
    BYTE	0b01111000 
    BYTE	0b00111110   
    BYTE	0b00011100

; 2
	BYTE	0b00011000 ; diamon 
    BYTE	0b00111100
    BYTE	0b01111110
    BYTE	0b11111111
    BYTE	0b11111111
    BYTE	0b01111110
    BYTE	0b00111100
    BYTE	0b00011000
    BYTE    0b00000100 ; 7 
    BYTE    0b00000110
    BYTE    0b00000011
    BYTE    0b11000001
    BYTE    0b11100001
    BYTE    0b00110011
    BYTE    0b00011110
    BYTE    0b00001100

; 3
	BYTE	0b00011000 ; diamon 
    BYTE	0b00111100
    BYTE	0b01111110
    BYTE	0b11111111
    BYTE	0b11111111
    BYTE	0b01111110
    BYTE	0b00111100
    BYTE	0b00011000
	BYTE    0b10000011 ;  X
    BYTE    0b11000110
    BYTE    0b01101100
    BYTE    0b00111000
    BYTE    0b00111000
    BYTE    0b01101100
    BYTE    0b11000110
    BYTE    0b10000011

; 4
    BYTE    0b00000100 ; 7 
    BYTE    0b00000110
    BYTE    0b00000011
    BYTE    0b11000001
    BYTE    0b11100001
    BYTE    0b00110011
    BYTE    0b00011110
    BYTE    0b00001100
    BYTE	0b00011100 ; Heart 
    BYTE	0b00111110
    BYTE	0b01111000
    BYTE	0b11110000 
    BYTE	0b11110000
    BYTE	0b01111000 
    BYTE	0b00111110   
    BYTE	0b00011100

; 5 
    BYTE    0b00000100 ; 7 
    BYTE    0b00000110
    BYTE    0b00000011
    BYTE    0b11000001
    BYTE    0b11100001
    BYTE    0b00110011
    BYTE    0b00011110
    BYTE    0b00001100
	BYTE    0b10000011 ;  X
    BYTE    0b11000110
    BYTE    0b01101100
    BYTE    0b00111000
    BYTE    0b00111000
    BYTE    0b01101100
    BYTE    0b11000110
    BYTE    0b10000011

; 6 = Winner 
	BYTE    0b10000011 ;  X
    BYTE    0b11000110
    BYTE    0b01101100
    BYTE    0b00111000
    BYTE    0b00111000
    BYTE    0b01101100
    BYTE    0b11000110
    BYTE    0b10000011
	BYTE    0b10000011 ;  X
    BYTE    0b11000110
    BYTE    0b01101100
    BYTE    0b00111000
    BYTE    0b00111000
    BYTE    0b01101100
    BYTE    0b11000110
    BYTE    0b10000011

; EOF