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297 lines
7.7 KiB
ArmAsm
297 lines
7.7 KiB
ArmAsm
;
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; Ullrich von Bassewitz, 07.08.1998
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;
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; unsigned DbgDisAsm (char* buf, unsigned addr);
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; unsigned DbgDisAsm (unsigned addr);
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;
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;
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; Part of this code is taken from the Plus/4 machine language monitor
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; (TEDMon).
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;
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.import popax
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.import __hextab, OffsetTab, AdrFlagTab
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.import SymbolTab1, SymbolTab2, MnemoTab1, MnemoTab2
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; -------------------------------------------------------------------------
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; Equates for better readability
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.importzp sreg, tmp1, tmp2, tmp3, tmp4, ptr1, ptr2, ptr3
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BufIndex = tmp1 ; Index into output buffer
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OperandLen = tmp2 ; Length of operand
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BufLen = tmp3 ; Length of output buffer
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AdrFlagBuf = tmp4 ; Flag for addressing mode
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YSave = sreg ; Temp storage
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XSave = sreg+1 ; Dito
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BufPtr = ptr1 ; Pointer to output buffer
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MemPtr = ptr2 ; Pointer to memory to disassemble
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MnemoBuf = ptr3 ; Buffer for decoding mnemonic
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; -------------------------------------------------------------------------
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; Main entries
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.export _DbgDisAsm, _DbgDisAsmLen
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.proc _DbgDisAsm
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sta BufLen ; Save the buffer length
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jsr popax ; Get the buffer pointer
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sta BufPtr
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stx BufPtr+1
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jsr popax ; Get the address
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sta MemPtr
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stx MemPtr+1
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lda #0
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sta BufIndex ; Initialize index into buffer
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jsr DisAssLine ; Disassemble one line into the buffer
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lda BufLen ; Get requested length
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sec
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sbc BufIndex
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beq L2
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tax ; Count into X
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ldy BufIndex
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lda #$20 ; Get a space
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L1: sta (BufPtr),y
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iny
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dex
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bne L1
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L2: lda #0 ; Add C string terminator
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sta (BufPtr),y
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beq disassret
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.endproc
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_DbgDisAsmLen:
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sta MemPtr ; Save address
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stx MemPtr+1
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ldy #$00
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lda (MemPtr),y ; Get the opcode from memory...
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jsr AnalyzeOPCode ; ...and analyze it
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disassret:
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ldx OperandLen ; Get length of operand
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inx ; Adjust for opcode byte
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txa
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ldx #$00 ; Clear high byte
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rts
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; -------------------------------------------------------------------------
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; Helper functions
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Put3Spaces:
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jsr PutSpace
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Put2Spaces:
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jsr PutSpace
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PutSpace:
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lda #$20
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PutChar:
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sty YSave ; Save Y
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ldy BufIndex ; Get current line pointer
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cpy BufLen ; Be sure not to overflow the buffer
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bcs PC9
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sta (BufPtr),y ; store character
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iny ; bump index
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sty BufIndex
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PC9: ldy YSave ; get old value
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rts
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; Print the 16 bit hex value in X/Y
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PutHex16:
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txa
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jsr PutHex8
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tya
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; Print 8 bit value in A, save X and Y
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PutHex8:
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stx XSave
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sty YSave
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ldy BufIndex
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pha
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lsr a
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lsr a
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lsr a
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lsr a
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tax
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lda __hextab,x
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sta (BufPtr),y
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iny
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pla
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and #$0F
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tax
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lda __hextab,x
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sta (BufPtr),y
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iny
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sty BufIndex
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ldy YSave
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ldx XSave
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rts
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; -------------------------------------------------------------------------
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; Disassemble one line
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DisAssLine:
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ldy MemPtr
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ldx MemPtr+1
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jsr PutHex16 ; Print the address
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jsr Put2Spaces ; Add some space
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ldy #$00
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lda (MemPtr),y ; Get the opcode from memory...
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jsr AnalyzeOPCode ; ...and analyze it
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pha ; Save mnemonic
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ldx OperandLen ; Number of bytes
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; Print the bytes that make up the instruction
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inx
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L2083: dex
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bpl L208C ; Print the instruction bytes
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jsr Put3Spaces ; If none left, print spaces instead
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jmp L2094
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L208C: lda (MemPtr),y ; Get a byte from memory
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jsr PutHex8 ; ...and print it
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jsr PutSpace ; Add some space
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L2094: iny ; Next one...
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cpy #$03 ; Maximum is three
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bcc L2083 ;
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jsr Put2Spaces ; Add some space after bytes
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; Print the assembler mnemonic
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pla ; Get mnemonic code
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ldx #$03
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jsr PutMnemo ; Print the mnemonic
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ldx #$06
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; Print the operand
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L20A4: cpx #$03
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bne L20BA
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ldy OperandLen
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beq L20BA
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L20AC: lda AdrFlagBuf
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cmp #$E8 ; Branch?
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lda (MemPtr),y ; Get branch offset
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bcs GetBranchAdr ; If branch: Calculate address
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jsr PutHex8 ; Otherwise print 8bit value
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dey
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bne L20AC
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L20BA: asl AdrFlagBuf
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bcc L20CC
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lda SymbolTab1-1,x
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jsr PutChar
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lda SymbolTab2-1,x
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beq L20CC
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jsr PutChar
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L20CC: dex
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bne L20A4
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rts
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; If the instruction is a branch, calculate the absolute address of the
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; branch target and print it.
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GetBranchAdr:
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jsr L20DD
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clc
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adc #$01
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bne L20D9
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inx ; Bump high byte
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L20D9: tay
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jmp PutHex16 ; Output address
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L20DD: ldx MemPtr+1
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tay
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bpl L20E3
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dex
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L20E3: adc MemPtr
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bcc L20E8
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inx ; Bump high byte
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L20E8: rts
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; -------------------------------------------------------------------------
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; Subroutine to analyze an opcode byte in A. Will return a byte that
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; encodes the mnemonic, and will set the number of bytes needed for this
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; instruction in OperandLen
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AnalyzeOPCode:
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tay
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lsr a
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bcc L20F8
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lsr a
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bcs L2107
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cmp #$22
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beq L2107
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and #$07
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ora #$80
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L20F8: lsr a
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tax
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lda OffsetTab,x
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bcs L2103
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lsr a
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lsr a
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lsr a
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lsr a
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L2103: and #$0F
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bne L210B
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L2107: ldy #$80
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lda #$00
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L210B: tax
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lda AdrFlagTab,x
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sta AdrFlagBuf
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and #$03
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sta OperandLen
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tya
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and #$8F
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tax
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tya
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ldy #$03
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cpx #$8A
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beq L212B
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L2120: lsr a
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bcc L212B
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lsr a
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L2124: lsr a
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ora #$20
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dey
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bne L2124
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iny
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L212B: dey
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bne L2120
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rts
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; -------------------------------------------------------------------------
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; Print the mnemonic with code in A (that code was returned by
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; AnalyzeOpcode).
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PutMnemo:
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tay
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lda MnemoTab1,y
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sta MnemoBuf
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lda MnemoTab2,y
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sta MnemoBuf+1
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L213A: lda #$00
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ldy #$05 ; 3*5 bits in two bytes
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L213E: asl MnemoBuf+1
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rol MnemoBuf
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rol a
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dey
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bne L213E
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adc #$3F
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jsr PutChar
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dex
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bne L213A
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jmp PutSpace
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