47 lines
964 B
ArmAsm
47 lines
964 B
ArmAsm
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.define Cms
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! This subroutine compares two groups of bytes, bit for bit.
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! The groups can consist of 2 or 4 bytes. This number is in
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! register Y.
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! The address of the first group is stored in zeropage locations
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! ADDR and ADDR+1, the address of the second group in ADDR+2 and ADDR+3
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! The routine returns a 0 on equality, a 1 otherwise.
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Cms:
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lda SP+2
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ldx SP+1
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sta ADDR ! address of first group (lowbyte)
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stx ADDR+1 ! address of second group (highbyte)
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clc
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tya
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adc SP+2
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sta SP+2
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sta ADDR+2 ! address of second group (lowbyte)
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txa
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adc #0
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sta ADDR+3 ! address of second group (highbyte)
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tax
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clc
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tya
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adc SP+2
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sta SP+2 ! new stackpointer (lowbyte)
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txa
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adc #0
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sta SP+1 ! new stackpointer (highbyte)
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1: dey
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lda (ADDR),y ! get byte first group
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cmp (ADDR+2),y ! compare bit for bit with byte second group
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bne 2f
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tya
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bne 1b
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lda #0 ! both groups are equal
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tax
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rts
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2: lda #0 ! there is a difference between the groups
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ldx #1
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rts
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