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page 66,264
cpu 6800
* = $1000
; memcpy --
; Copy a block of memory from one location to another.
; Called as a subroutine, note return to saved PC addr on exit
; Entry parameters
; cnt - Number of bytes to copy
; src - Address of source data block
; dst - Address of target data block
cnt dw $0000 ; sets aside space for memory addr
src dw $0000 ; sets aside space for memory addr
dst dw $0000 ; sets aside space for memory addr
memcpy ldab cnt+1 ;Set B = cnt.L
beq check ;If cnt.L=0, goto check
loop ldx src ;Set IX = src
ldaa ,x ;Load A from (src)
inx ;Set src = src+1
stx src
ldx dst ;Set IX = dst
staa ,x ;Store A to (dst)
inx ;Set dst = dst+1
stx dst
decb ;Decr B
bne loop ;Repeat the loop
stab cnt+1 ;Set cnt.L = 0
check tst cnt+0 ;If cnt.H=0,
beq done ;Then quit
dec cnt+0 ;Decr cnt.H
; loop back and do 256*(cnt.H+1) more copies (B=0)
bra loop ;Repeat the loop
done rts ;Return
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