134 lines
1.8 KiB
ArmAsm
134 lines
1.8 KiB
ArmAsm
;
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; utility.s
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; General utilities for 6502
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;
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; Created by Quinn Dunki on 8/15/14.
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; Copyright (c) 2014 One Girl, One Laptop Productions. All rights reserved.
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;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; delay
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; Sleeps for ~1 second
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;
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delay:
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SAVE_AXY
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ldy #$ce ; Loop a bunch
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delayOuter:
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ldx #$ff
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delayInner:
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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dex
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bne delayInner
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dey
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bne delayOuter
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RESTORE_AXY
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rts
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; delayShort
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; Sleeps for ~1/30th second
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;
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delayShort:
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SAVE_AXY
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ldy #$06 ; Loop a bit
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delayShortOuter:
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ldx #$ff
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delayShortInner:
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nop
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nop
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nop
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nop
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nop
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nop
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nop
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dex
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bne delayShortInner
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dey
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bne delayShortOuter
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RESTORE_AXY
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rts
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;;;;;;;;;;;;;;;;;;;;;;;
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; scanHexDigit
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; Scans a 4 bit hex value from an ASCII character
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; A: ASCII character
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; Out A: Hex value
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;
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scanHexDigit:
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cmp #'A'
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bcs scanHexDigitLetter
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sec
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sbc #'0'
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jmp scanHexDigitDone
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scanHexDigitLetter:
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sec
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sbc #55
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scanHexDigitDone:
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rts
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;;;;;;;;;;;;;;;;;;;;;;;
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; scanHex8
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; Scans an 8 bit hex value from a string
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; PARAM0: Pointer to string (LSB)
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; PARAM1: Pointer to string (MSB)
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; Y: Offset into string
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; Out A: 8-bit hex value
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; Side effects: Clobbers Y and S0
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;
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scanHex8:
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lda (PARAM0),y
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jsr scanHexDigit
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asl
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asl
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asl
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asl
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sta SCRATCH0 ; Stash first digit for later
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iny
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lda (PARAM0),y
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jsr scanHexDigit
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ora SCRATCH0
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iny ; Be nice and advance Y to end
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rts
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; WGStrLen
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; Finds the length of a null-terminated string
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; PARAM0: String pointer, LSB
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; PARAM1: String pointer, MSB
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; Return: A: String length, not including null
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;
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WGStrLen:
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phy
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ldy #$0
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WGStrLen_loop:
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lda (PARAM0),y
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beq WGStrLen_done
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iny
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bra WGStrLen_loop
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WGStrLen_done:
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tya
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ply
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rts
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