; Fibonacci Benchmark for Competition
;
; Wettkampf Opa(MOS6502) gegen Frischling(ATmega)
;
; https://www.mikrocontroller.net/topic/577155
;
; 2025-04-21 by mchris
;
; remark: further optimizations are possbile ..
;

        org $C000          ; Start of the program

OutputAddress = $F001

Start:
        LDA #0
        STA 0 ; store initial value in NumberB
        LDA #1 
        STA 40 ; store initial value in NumberB

        ;JSR PrintA
        ;JSR PrintB
        ; max iterations is 382
        ; for this loop we need the half: 191
        LDY #191              ; Fibonacci order n-times
LOOP1:        
        JSR AddA
        ;JSR PrintA

        JSR AddB
        ;JSR PrintB

        DEY
        BNE LOOP1
        
        ; this is the largest number:
        JSR AddA
        JSR PrintA

        BRK

        
;-------------------------------
; Subroutine: BCD_TO_ASCII
;
; input: ACC
;
; one byte storage: ascii_lo
;
;-------------------------------
BCD_TO_ASCII:
        PHA ; push acc
        ; --- Low nibble to ASCII ---
        AND #$0F             ; Mask low nibble
        CLC
        ADC #$30             ; Convert to ASCII
        STA ascii_lo         ; Store as low digit

        ; --- High nibble to ASCII ---
        PLA ; pop ACC
        LSR A                ; Shift right 4 times
        LSR A
        LSR A
        LSR A
        AND #$0F             ; Mask high nibble
        CLC
        ADC #$30             ; Convert to ASCII
        STA $F001            ; print acc
        LDA ascii_lo
        STA $F001            ; print acc
        
        RTS                  ; Return from subroutine
        
;******************** PRINT BCD ****************************************************
PrintA:
        LDX #39                ; Start at most significant digit (index 9)
PrintLoop:
        LDA 0,X
        CLC
        JSR BCD_TO_ASCII

        DEX
        BPL PrintLoop       ; Loop while X >= 0

        LDA #$20 ; space
        STA Screen
        
        LDA #$0A ; line feed
        STA Screen

        RTS                 ; End program

PrintB:
        LDX #39                ; Start at most significant digit (index 9)
PrintLoopB:
        LDA 40,X ; adr NumB
        CLC
        JSR BCD_TO_ASCII

        DEX
        BPL PrintLoopB       ; Loop while X >= 0

        LDA #$20 ; space
        STA Screen
        
        LDA #$0A ; line feed
        STA Screen

        RTS                 ; End program

;******************** ADD BCD A  ****************************************************
AddA:
        SED             ; Set Decimal Mode for BCD operations
        CLC             ; Clear carry before addition
        ;LDX #0          ; Start from the least significant digit

AddLoopA:

        LDA 0
	ADC 40
	STA 0

	LDA 1
	ADC 41
	STA 1

	LDA 2
	ADC 42
	STA 2

	LDA 3
	ADC 43
	STA 3

	LDA 4
	ADC 44
	STA 4
;##
        LDA 5
	ADC 45
	STA 5

	LDA 6
	ADC 46
	STA 6

	LDA 7
	ADC 47
	STA 7

	LDA 8
	ADC 48
	STA 8

	LDA 9
	ADC 49
	STA 9
;###

        LDA 10
	ADC 50
	STA 10

	LDA 11
	ADC 51
	STA 11

	LDA 12
	ADC 52
	STA 12

	LDA 13
	ADC 53
	STA 13

	LDA 14
	ADC 54
	STA 14
;##
        LDA 15
	ADC 55
	STA 15

	LDA 16
	ADC 56
	STA 16

	LDA 17
	ADC 57
	STA 17

	LDA 18
	ADC 58
	STA 18

	LDA 19
	ADC 59
	STA 19
;#####

        LDA 20
	ADC 60
	STA 20

	LDA 21
	ADC 61
	STA 21

	LDA 22
	ADC 62
	STA 22

	LDA 23
	ADC 63
	STA 23

	LDA 24
	ADC 64
	STA 24
;##
        LDA 25
	ADC 65
	STA 25

	LDA 26
	ADC 66
	STA 26

	LDA 27
	ADC 67
	STA 27

	LDA 28
	ADC 68
	STA 28

	LDA 29
	ADC 69
	STA 29
;###

        LDA 30
	ADC 70
	STA 30

	LDA 31
	ADC 71
	STA 31

	LDA 32
	ADC 72
	STA 32

	LDA 33
	ADC 73
	STA 33

	LDA 34
	ADC 74
	STA 34
;##
        LDA 35
	ADC 75
	STA 35

	LDA 36
	ADC 76
	STA 36

	LDA 37
	ADC 77
	STA 37

	LDA 38
	ADC 78
	STA 38

	LDA 39
	ADC 79
	STA 39
;#####


        CLD             ; Clear decimal mode (optional)

        RTS

;******************** ADD BCD B  ****************************************************
AddB:
        SED             ; Set Decimal Mode for BCD operations
        CLC             ; Clear carry before addition
        LDX #0          ; Start from the least significant digit

AddLoopB:
        LDA 0
	ADC 40
	STA 40

	LDA 1
	ADC 41
	STA 41

	LDA 2
	ADC 42
	STA 42

	LDA 3
	ADC 43
	STA 43
	
        LDA 4
	ADC 44
	STA 44
;##
	LDA 5
	ADC 45
	STA 45

	LDA 6
	ADC 46
	STA 46

	LDA 7
	ADC 47
	STA 47

	LDA 8
	ADC 48
	STA 48

	LDA 9
	ADC 49
	STA 49
;####
        LDA 10
	ADC 50
	STA 50

	LDA 11
	ADC 51
	STA 51

	LDA 12
	ADC 52
	STA 52

	LDA 13
	ADC 53
	STA 53
	
        LDA 14
	ADC 54
	STA 54
;##
	LDA 15
	ADC 55
	STA 55

	LDA 16
	ADC 56
	STA 56

	LDA 17
	ADC 57
	STA 57

	LDA 18
	ADC 58
	STA 58

	LDA 19
	ADC 59
	STA 59
;####
        LDA 20
	ADC 60
	STA 60

	LDA 21
	ADC 61
	STA 61

	LDA 22
	ADC 62
	STA 62

	LDA 23
	ADC 63
	STA 63
	
        LDA 24
	ADC 64
	STA 64
;##
	LDA 25
	ADC 65
	STA 65

	LDA 26
	ADC 66
	STA 66

	LDA 27
	ADC 67
	STA 67

	LDA 28
	ADC 68
	STA 68

	LDA 29
	ADC 69
	STA 69
;####
        LDA 30
	ADC 70
	STA 70

	LDA 31
	ADC 71
	STA 71

	LDA 32
	ADC 72
	STA 72

	LDA 33
	ADC 73
	STA 73
	
        LDA 34
	ADC 74
	STA 74
;##
	LDA 35
	ADC 75
	STA 75

	LDA 36
	ADC 76
	STA 76

	LDA 37
	ADC 77
	STA 77

	LDA 38
	ADC 78
	STA 78

	LDA 39
	ADC 79
	STA 79
;##



        CLD             ; Clear decimal mode (optional)

        RTS        

; === BCD number: 1234567890 ===
        org $0000
NumA: 
        db $00,$00,$00,$00,$00,$00,$00,$00,$00,$00  ; LSB first
        db $00,$00,$00,$00,$00,$00,$00,$00,$00,$00  ; LSB first
        db $00,$00,$00,$00,$00,$00,$00,$00,$00,$00  ; LSB first
        db $00,$00,$00,$00,$00,$00,$00,$00,$00,$00  ; LSB first

NumB: 
        db $00,$00,$00,$00,$00,$00,$00,$00,$00,$00  ; LSB first
        db $00,$00,$00,$00,$00,$00,$00,$00,$00,$00  ; LSB first
        db $00,$00,$00,$00,$00,$00,$00,$00,$00,$00  ; LSB first
        db $00,$00,$00,$00,$00,$00,$00,$00,$00,$00  ; LSB first


ascii_lo:  db 0           ; Output: ASCII low digit
        org $F001
Screen: