63 lines
964 B
ArmAsm
63 lines
964 B
ArmAsm
;; printf()-like routine for simplifying debugging
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;; Prints the literal zero-terminated string that follows,
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;; which may also include special tokens that allow
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;; printing of hex byte and word values stored at the indicated
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;; addresses.
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printf:
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;; Temporary storage is between end of screen at $0400
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;; and the sprite pointers at $7f8
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sta $7f0
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stx $7f1
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sty $7f2
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php
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pla
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sta $7f3
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;; Set up read routine
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lda #$ad ; LDA $nnnn
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sta $7f4
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lda #$60
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sta $7f7 ; RTS
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;; Get PC of caller from the stack, so that
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;; we can parse through it
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pla
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clc
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adc #$01
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sta $7f5
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pla
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adc #$00
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sta $7f6
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printf_loop:
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jsr $7f4
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cmp #$00
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bne printf_continues
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;; Put return address on stack and restore
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;; registers
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lda $7f6
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pha
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lda $7f5
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pha
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lda $7f3
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pha
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lda $7f0
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ldx $7f1
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ldy $7f2
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plp
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rts
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printf_continues:
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;; Print character
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jsr $ffd2
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printf_nextchar:
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;; Advance pointer to next character
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inc $7f5
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bne +
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inc $7f6
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*
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jmp printf_loop
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