define StringRam $1200
define BitRam $1400
define z_BC $00
define z_C $00
define z_B $01
define z_DE $02
define z_E $02
define z_D $03
define tempMath $04
define tempBitMask $05
define tempY $06
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
LDA #0
TAX
TAY                 ;clear data regs (not needed on Easy6502 but it's a good practice at the start of a program on real hardware)

loop_clearRam:
STA $1200,x
STA $1400,x
inx
bne loop_clearRam

lda #$12
sta z_B
lda #$00
sta z_C

lda #$57
jsr Hex2BinAscii     ;store first string

lda #$50
jsr Hex2BinAscii    ; store second string
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
LDA #$12
STA z_B
LDA #$00
STA z_C             ; get address of string Ram (this step isn't necessary as they're already loaded but it's here for clarity)

LDA #$14
STA z_D
LDA #$00
STA z_E             ; get address of destination

LDY #$00
STY tempY           ; the indices into StringRam and BitRam are different.

jsr CompressBits
brk

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
Hex2BinAscii:
; this procedure is the same as the above example.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
CompressBits:
; takes a stream of ascii zeroes and ones,
; and packs them into a series of bytes.

LDX #8            ; repeat 8 times.
LDA #0
STA tempMath      ;zero out tempMath
;;;;;;;;;;;;;;;;;;;;;;;;;
loop_CompressBits:
LDA (z_BC),y
beq Terminated    ; if the value read is equal to the null terminator, we are done.
                  ; value is assumed to equal #$30 for 0 or #$31 for 1.
ror               ; bottom bit of accumulator is rotated into the carry flag.
rol tempMath      ; the carry is shifted into the bottom of tempMath.
; repeating this with each successive ascii bit representation
; will preserve the order of the bits. It's hard to explain without drawing a picture
; but trust me it just works.
iny               ; next Y
dex
bne loop_CompressBits
;;;;;;;;;;;;;;;;;;;;;;;;;
; loop overhead
tya
pha               ; backup source index.
   ldy tempY
   lda tempMath
   sta (z_DE),y
   inc tempY      ; increment destination index
pla
tay               ; restore source index
jmp CompressBits  ; back to top
;;;;;;;;;;;;;;;;;;;;;;;;;
Terminated:
rts