Document disassembler
This commit is contained in:
J.B. Langston
+82
-82
@@ -558,8 +558,8 @@ ASQEEZ DEX ; move to previous char
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SBC #$3F ; subtract $3F from ascii code so A-Z = 2 to 27
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LDY #$05 ; letters now fit in 5 bits; shift them out
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ASHIFT LSR A ; into the first two bytes of the inst buffer
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ROR U0AA0+1 ; catch the low bit from accumulator in U0AA0[1]
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ROR U0AA0 ; catch the low bit from high byte in U0AA0[0]
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ROR U0AA0+1 ; catch the low bit from accumulator in right byte
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ROR U0AA0 ; catch the low bit from right byte in left byte
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DEY ; count down bits
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BNE ASHIFT ; keep looping until we reach zero
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BEQ ASQEEZ ; unconditional branch to handle next char
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@@ -671,13 +671,13 @@ ABRANX DEX ; adjust branch target relative to the
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DEX ; instruction following this one
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TXA
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LDY LENGTH ; load length of operand
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BNE OBJP2
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BNE OBJP2 ; don't use the absolute address
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; assemble machine code
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OBJPUT LDA TMP0-1,Y ; put bytes from operand into instruction
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OBJP2 STA (TMP2),Y
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OBJPUT LDA TMP0-1,Y ; get the operand
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OBJP2 STA (TMP2),Y ; store it after the opcode
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DEY
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BNE OBJPUT
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BNE OBJPUT ; copy the other byte of operand if there is one
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A1BYTE LDA OPCODE ; put opcode into instruction
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STA (TMP2),Y
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JSR CRLF ; carriage return
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@@ -702,10 +702,10 @@ A1BYTE LDA OPCODE ; put opcode into instruction
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JSR ASCTWO
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STA KEYD+4 ; put it in the keyboard buffer
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STX KEYD+5
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LDA #7
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LDA #7 ; set number of chars in keyboard buffer
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STA NDX
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JMP STRT
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SERROR JMP ERROR
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JMP STRT ; back to main loop
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SERROR JMP ERROR ; handle error
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; check characters in operand
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CHEK2B JSR CHEKOP ; check two bytes against value in accumulator
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@@ -724,95 +724,95 @@ OPOK INC U9F ; opcode matches so far; check the next criteria
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; -----------------------------------------------------------------------------
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; disassemble [D]
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DISASS BCS DIS0AD
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JSR COPY12
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JSR GETPAR
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BCC DIS2AD
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DIS0AD LDA #$14
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STA TMP0
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BNE DISGO
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DIS2AD JSR SUB12
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BCC DERROR
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DISGO JSR CLINE
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JSR STOP
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BEQ DISEXIT
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JSR DSOUT1
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DISASS BCS DIS0AD ; if no address was given, start from last address
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JSR COPY12 ; copy start address to TMP2
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JSR GETPAR ; get end address in TMP0
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BCC DIS2AD ; if one was given, skip default
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DIS0AD LDA #$14 ; disassemble 14 bytes by default
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STA TMP0 ; store length in TMP0
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BNE DISGO ; skip length calculation
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DIS2AD JSR SUB12 ; calculate number of bytes between start and end
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BCC DERROR ; error if end address is before start address
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DISGO JSR CLINE ; clear the current line
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JSR STOP ; check for stop key
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BEQ DISEXIT ; exit early if pressed
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JSR DSOUT1 ; output disassembly prefix ". "
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INC LENGTH
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LDA LENGTH
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LDA LENGTH ; add length of last instruction to start address
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JSR BUMPAD2
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LDA LENGTH
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LDA LENGTH ; subtract length of last inst from end address
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JSR SUBA2
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BCS DISGO
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DISEXIT JMP STRT
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DISEXIT JMP STRT ; back to mainloop
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DERROR JMP ERROR
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DSOUT1 LDA #"."
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DSOUT1 LDA #"." ; output ". " prefix to allow edit and reassemble
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JSR CHROUT
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JSR SPACE
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DISLIN JSR SHOWAD
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JSR SPACE
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LDY #0
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LDA (TMP2),Y
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JSR INSTXX
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PHA
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LDX LENGTH
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INX
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DSBYT DEX
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BPL DSHEX
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STY SAVY
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LDY #MSG8-MSGBAS
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DISLIN JSR SHOWAD ; show the address of the instruction
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JSR SPACE ; insert a space
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LDY #0 ; no offset
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LDA (TMP2),Y ; load operand of current instruction
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JSR INSTXX ; get mnemonic and addressing mode for opcode
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PHA ; save index into mnemonic table
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LDX LENGTH ; get length of operand
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INX ; add 1 byte for opcode
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DSBYT DEX ; decrement index
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BPL DSHEX ; show hex for byte being disassembled
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STY SAVY ; save index
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LDY #MSG8-MSGBAS ; skip 3 spaces
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JSR SNDMSG
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LDY SAVY
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LDY SAVY ; restore index
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JMP NXBYT
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DSHEX LDA (TMP2),Y
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DSHEX LDA (TMP2),Y ; show hex for byte
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JSR WRBYTE
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NXBYT INY
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CPY #3
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BCC DSBYT
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PLA
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LDX #3
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JSR PROPXX
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LDX #6
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PRADR1 CPX #3
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BNE PRADR3
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LDY LENGTH
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BEQ PRADR3
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PRADR2 LDA ACMD
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CMP #$E8
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PHP
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LDA (TMP2),Y
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PLP
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BCS RELAD
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JSR WRTWO
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NXBYT INY ; next byte
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CPY #3 ; have we output 3 bytes yet?
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BCC DSBYT ; if not, loop
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PLA ; restore index into mnemonic table
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LDX #3 ; 3 letters in mnemonic
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JSR PROPXX ; print mnemonic
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LDX #6 ; 6 possible address mode character combos
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PRADR1 CPX #3 ; have we checked the third combo yet?
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BNE PRADR3 ; if so, output the leading characters
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LDY LENGTH ; get the length of the operand
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BEQ PRADR3 ; if it's zero, there's no operand to print
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PRADR2 LDA ACMD ; otherwise, get the addressing mode
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CMP #$E8 ; check for relative addressing
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PHP ; save result of check
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LDA (TMP2),Y ; get the operand
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PLP ; restore result of check
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BCS RELAD ; handle a relative address
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JSR WRTWO ; output digits from address
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DEY
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BNE PRADR2
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PRADR3 ASL ACMD
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BCC PRADR4
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LDA CHAR1-1,X
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JSR CHROUT
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LDA CHAR2-1,X
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BEQ PRADR4
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JSR CHROUT
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PRADR4 DEX
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BNE PRADR1
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RTS
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RELAD JSR UB64D
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BNE PRADR2 ; repeat for next byte of operand, if there is one
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PRADR3 ASL ACMD ; check whether addr mode uses the current char
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BCC PRADR4 ; if not, skip it
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LDA CHAR1-1,X ; look up the first char in the table
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JSR CHROUT ; print first char
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LDA CHAR2-1,X ; look up the second char in the table
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BEQ PRADR4 ; if there's no second character, skip it
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JSR CHROUT ; print second char
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PRADR4 DEX ; next potential address mode character
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BNE PRADR1 ; loop if we haven't checked them all yet
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RTS ; back to caller
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RELAD JSR UB64D ; calculate absolute address from relative
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CLC
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ADC #1
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BNE RELEND
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INX
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RELEND JMP WRADDR
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ADC #1 ; adjust address relative to next instruction
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BNE RELEND ; don't increment high byte unless we overflowed
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INX ; increment high byte
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RELEND JMP WRADDR ; print address
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UB64D LDX TMP2+1
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TAY
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BPL RELC2
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DEX
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RELC2 ADC TMP2
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BCC RELC3
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INX
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RELC3 RTS
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UB64D LDX TMP2+1 ; get high byte of current address
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TAY ; is relative address positive or negative?
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BPL RELC2 ; if positive, leave high byte alone
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DEX ; if negative, decrement high byte
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RELC2 ADC TMP2 ; add relative address to low byte
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BCC RELC3 ; if there's no carry, we're done
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INX ; if there's a carry, increment the high byte
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RELC3 RTS
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; -----------------------------------------------------------------------------
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; get opcode mode and length
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