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EA.X68
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2000 lines (1990 loc) · 101 KB
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*-----------------------------------------------------------
* Title : Effective Addressing Subroutines
* Written by : Brandon Authier (Hblkr), Jack S. Eldridge
* (JackScottie), Marijn Burger (marijnburger)
* Date : 16 May 2016
* Description: Support file containing the effective
* addressing subroutines for the disassembler.
*-----------------------------------------------------------
*-- Definitions Used for Code ------------------------------
INCLUDE 'EA_UTIL.X68'
*-- Subroutines: -------------------------------------------
*---------- ADD Effective Addresses ------------------------
* Parses and prints the effective addressing information for
* the ADD opcode
*-----------------------------------------------------------
EA_ADD:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to A5
JSR EA_OPMODE_COMBO ; opmode: D6, register: D7
LEA ADD_OPMODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
*--- determine mode: mode 1 is '<ea>, Dn', mode 2 is 'Dn, <ea>'
ADD_OPMODE:
JMP ADD_OPMODE_000 ; mode 1, byte
JMP ADD_OPMODE_001 ; mode 1, word
JMP ADD_OPMODE_010 ; mode 1, long
JMP ADD_OPMODE_011 ; Invalid value
JMP ADD_OPMODE_100 ; mode 2, byte
JMP ADD_OPMODE_101 ; mode 2, word
JMP ADD_OPMODE_110 ; mode 2, long
JMP ADD_OPMODE_111 ; Invalid value
*-----------------------------------
*--- Opmode jump table options -----
ADD_OPMODE_000: ; mode 1, byte
MOVE.B #1, D5 ; Store size in the case of an immediate operand
JMP ADD_MODE_1
ADD_OPMODE_001: ; mode 1, word
MOVE.B #2, D5 ; Store size in the case of an immediate operand
JMP ADD_MODE_1
ADD_OPMODE_010: ; mode 1, long
MOVE.B #3, D5 ; Store size in the case of an immediate operand
JMP ADD_MODE_1
ADD_OPMODE_011: ; Invalid value
JSR EA_INVALID
JMP ADD_END
ADD_OPMODE_100: ; mode 2, byte
MOVE.B #1, D5 ; Store size in the case of an immediate operand
JMP ADD_MODE_2
ADD_OPMODE_101: ; mode 2, word
MOVE.B #1, D5 ; Store size in the case of an immediate operand
JMP ADD_MODE_2
ADD_OPMODE_110: ; mode 2, long
MOVE.B #1, D5 ; Store size in the case of an immediate operand
JMP ADD_MODE_2
ADD_OPMODE_111: ; Invalid value
JSR EA_INVALID
JMP ADD_END
*-----------------------------------
*--- Mode 1 ------------------------
ADD_MODE_1:
CLR.L D0 ; Clear data register 0
MOVE.B #1, D0 ; Save mode number to D0
MOVE.W D7, D1 ; Save register value for printing dest. operand
JSR EA_DEFAULT_COMBO ; Stores mode bits in D6, register bits in D7
JSR ADD_EVAL_EA ; Evaluate the results of subroutine call
CMP.B #$01, D4 ; Check if EA bits were invalid
BEQ ADD_MODE_1_END ; If invalid, skip printing destination
LEA COMMA, A4 ; Else, print comma
JSR WRITE2MEM
MOVE.W D1, D7 ; Return register value to D7 for use by subroutine
JSR EA_PRINT_DN ; Print data register
ADD_MODE_1_END:
JMP ADD_END
*-----------------------------------
*--- Mode 2 ------------------------
ADD_MODE_2:
CLR.L D0 ; Clear data register 0
MOVE.B #2, D0 ; Save mode number to D0
JSR EA_PRINT_DN ; Print data register
LEA COMMA, A4 ; Print comma
JSR WRITE2MEM
JSR EA_DEFAULT_COMBO ; Stores mode bits in D6, register bits in D7
JSR ADD_EVAL_EA ; Evaluate the results of subroutine call
JMP ADD_END
*-----------------------------------
*--- Evaluate EA bits --------------
ADD_EVAL_EA:
LEA ADD_MODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
*--- Check validity based on mode value
ADD_MODE:
JMP ADD_MODE_000 ; Dn (invalid if opmode 2)
JMP ADD_MODE_001 ; An (invalid if opmode 2)
JMP ADD_MODE_010 ; (An)
JMP ADD_MODE_011 ; (An)+
JMP ADD_MODE_100 ; -(An)
JMP ADD_MODE_101 ; Invalid: Address Register Indirect with Displacement Mode
JMP ADD_MODE_110 ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP ADD_MODE_111 ; The rest (not all valid, validated by register number)
*-----------------------------------
*--- EA mode jump table options ----
ADD_MODE_000: ; Dn (invalid if opmode 2)
CMP #2, D0
BEQ ADD_MODE_INVALID ; If opmode 2, Dn is invalid addressing mode
JSR EA_PRINT_DN ; Print data register direct operand
JMP ADD_MODE_END ; End evaluation of ea mode
ADD_MODE_001: ; An (invalid if opmode 2)
CMP #2, D0
BEQ ADD_MODE_INVALID ; If opmode 2, An is invalid addressing mode
JSR EA_PRINT_AN ; Address register direct is invalid mode
JMP ADD_MODE_END ; End evaluation of ea mode
ADD_MODE_010: ; (An)
JSR EA_PRINT_IND ; Print address register indirect
JMP ADD_MODE_END ; End evaluation of ea mode
ADD_MODE_011: ; (An)+
JSR EA_PRINT_POSTINC ; Print address register indirect with post increment
JMP ADD_MODE_END ; End evaluation of ea mode
ADD_MODE_100: ; -(An)
JSR EA_PRINT_PREDEC ; Print address register indirect with pre decrement
JMP ADD_MODE_END ; End evaluation of ea mode
ADD_MODE_101: ; Invalid: Address Register Indirect with Displacement Mode
JMP ADD_MODE_INVALID
ADD_MODE_110: ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP ADD_MODE_INVALID
ADD_MODE_111: ; The rest (not all valid, validated by register number)
CMP.B #$00, D7 ; Test for absolute word address
BEQ ADD_ABS_W
CMP.B #$01, D7 ; Test for absolute long address
BEQ ADD_ABS_L
CMP.B #$04, D7 ; Test for immediate data
BEQ ADD_IMM
JMP ADD_MODE_INVALID ; else, invalid
*-----------------------------------
*--- Valid options for mode 111 ----
ADD_ABS_W:
JSR EA_PRINT_ABS_W ; Print absolute word address operand
JMP ADD_MODE_END
ADD_ABS_L:
JSR EA_PRINT_ABS_L ; Print absolute long address operand
JMP ADD_MODE_END
ADD_IMM: ; invalid if opmode is 2
CMP #2, D0
BEQ ADD_MODE_INVALID ; If opmode 2, An is invalid addressing mode
JSR EA_PRINT_IMM ; Print immediate data
JMP ADD_MODE_END
*-----------------------------------
ADD_MODE_END:
RTS ; Finish evaluating EA bits
ADD_MODE_INVALID:
JSR EA_INVALID ; Opcode word is Invalid
MOVE.B #$01, D4 ; Store flag to indicate invalidity, for mode 1
JMP ADD_MODE_END
*-----------------------------------
ADD_END:
JSR EA_UPDATE_POINTER ; Updates global pointer
MOVEM.L (SP)+, A0-A1/A3-A5/D0-D7 ; Restore registers (except A6, global pointer to word to read)
RTS
*---------- ADDA Effective Addresses -----------------------
* Parses and prints the effective addressing information for
* the ADDA opcode
*-----------------------------------------------------------
EA_ADDA:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to A5
JSR EA_DEFAULT_COMBO ; Mode: D6, register: D7
LEA ADDA_MODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
*--- Check validity based on mode value
ADDA_MODE:
JMP ADDA_MODE_000 ; Dn
JMP ADDA_MODE_001 ; An
JMP ADDA_MODE_010 ; (An)
JMP ADDA_MODE_011 ; (An)+
JMP ADDA_MODE_100 ; -(An)
JMP ADDA_MODE_101 ; Invalid: Address Register Indirect with Displacement Mode
JMP ADDA_MODE_110 ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP ADDA_MODE_111 ; The rest (not all valid, validated by register number)
*-----------------------------------
*--- EA mode jump table options ----
ADDA_MODE_000: ; Dn
JSR EA_PRINT_DN ; Print data register direct operand
JMP ADDA_MODE_END ; End evaluation of ea mode
ADDA_MODE_001: ; An
JSR EA_PRINT_AN ; Address register direct is invalid mode
JMP ADDA_MODE_END ; End evaluation of ea mode
ADDA_MODE_010: ; (An)
JSR EA_PRINT_IND ; Print address register indirect
JMP ADDA_MODE_END ; End evaluation of ea mode
ADDA_MODE_011: ; (An)+
JSR EA_PRINT_POSTINC ; Print address register indirect with post increment
JMP ADDA_MODE_END ; End evaluation of ea mode
ADDA_MODE_100: ; -(An)
JSR EA_PRINT_PREDEC ; Print address register indirect with pre decrement
JMP ADDA_MODE_END ; End evaluation of ea mode
ADDA_MODE_101: ; Invalid: Address Register Indirect with Displacement Mode
JMP ADDA_MODE_INVALID
ADDA_MODE_110: ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP ADDA_MODE_INVALID
ADDA_MODE_111: ; The rest (not all valid, validated by register number)
CMP.B #$00, D7 ; Test for absolute word address
BEQ ADDA_ABS_W
CMP.B #$01, D7 ; Test for absolute long address
BEQ ADDA_ABS_L
CMP.B #$04, D7 ; Test for immediate data
BEQ ADDA_IMM
JMP ADDA_MODE_INVALID ; Else, invalid
*-----------------------------------
*--- Valid options for mode 111 ----
ADDA_ABS_W:
JSR EA_PRINT_ABS_W ; Print absolute word address operand
JMP ADDA_MODE_END
ADDA_ABS_L:
JSR EA_PRINT_ABS_L ; Print absolute long address operand
JMP ADDA_MODE_END
ADDA_IMM:
JSR EA_OPMODE_COMBO ; Get opmode bits in
CMP.B #7, D6 ; Test if longword operation
BEQ ADDA_IMM_L ; If longword, set size to longword
MOVE.L #2, D5 ; Else, set size to word
JMP ADDA_IMM_END
ADDA_IMM_L:
MOVE.L #3, D5 ; Set size to longword
ADDA_IMM_END:
JSR EA_PRINT_IMM ; Print immediate data
JMP ADDA_MODE_END
*-----------------------------------
ADDA_MODE_INVALID:
JSR EA_INVALID ; Opcode word is Invalid
JMP ADDA_END
ADDA_MODE_END:
LEA COMMA, A4 ; Print comma
JSR WRITE2MEM
JSR EA_OPMODE_COMBO ; Opmode: D6, register: D7
JSR EA_PRINT_AN ; Print address register
ADDA_END:
JSR EA_UPDATE_POINTER ; Update global pointer
MOVEM.L (SP)+, A0-A1/A3-A5/D0-D7 ; Restore registers (except A6, global pointer to word to read)
RTS
*---------- ADDI Effective Addresses -----------------------
* Parses and prints the effective addressing information for
* the ADDI opcode
*-----------------------------------------------------------
EA_ADDI:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to A5
LEA POUND, A4 ; Print '#'
JSR WRITE2MEM
LEA DOLLAR, A4 ; Print '$'
JSR WRITE2MEM
JSR EA_SIZE_BITS ; get size bits in D7
*--- Branch based on size ----------
CMP.B #$00, D7 ; Test if size: byte
BEQ ADDI_B
CMP.B #$01, D7 ; Test if size: word
BEQ ADDI_W
CMP.B #$02, D7 ; Test if size: long
BEQ ADDI_L
JSR EA_INVALID ; Else, invalid
JMP ADDI_END
*--- Print immediate data ----------
ADDI_B:
ADDA.L #$00000002, A5 ; Increment A5 past current word
CLR.L D6
MOVE.W (A5), D6 ; read next word in memory and save
MOVE.B #8, D2 ; Clear upper 8 bits of operand word
LSL.W D2, D6 ; Perform shift (zeros shifted in)
MOVE.B #8, D2 ; 'Right-align' bits 0-7 to get value
LSR.W D2, D6 ; Perform shift (zeros shifted in)
MOVE.L #2, D7 ; set size to B
JSR WRITEDATA2MEM
ADDA.L #$00000002, A5 ; Increment A5 past operand word
JMP ADDI_GET_DEST
ADDI_W:
ADDA.L #$00000002, A5 ; Increment A5 past current word
CLR.L D0
MOVE.W (A5), D6 ; read next word in memory and save
MOVE.L #4, D7 ; set size to B
JSR WRITEDATA2MEM
ADDA.L #$00000002, A5 ; Increment A5 past operand word
JMP ADDI_GET_DEST
ADDI_L:
ADDA.L #$00000002, A5 ; Increment A5 past current word
MOVE.L (A5), D6 ; read next two words in memory and save
MOVE.L #8, D7 ; set size to B
JSR WRITEDATA2MEM
ADDA.L #$00000004, A5 ; Increment A5 past operand longword
*--- Get destination operand -------
ADDI_GET_DEST:
LEA COMMA, A4 ; Print comma
JSR WRITE2MEM
JSR EA_DEFAULT_COMBO ; get mode bits in D6, register bits in D7
LEA ADDI_MODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
*--- Check validity based on mode value
ADDI_MODE:
JMP ADDI_MODE_000 ; Dn
JMP ADDI_MODE_001 ; Invalid: An
JMP ADDI_MODE_010 ; (An)
JMP ADDI_MODE_011 ; (An)+
JMP ADDI_MODE_100 ; -(An)
JMP ADDI_MODE_101 ; Invalid: Address Register Indirect with Displacement Mode
JMP ADDI_MODE_110 ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP ADDI_MODE_111 ; The rest (not all valid, validated by register number)
*-----------------------------------
*--- EA mode jump table options ----
ADDI_MODE_000: ; Dn
JSR EA_PRINT_DN ; Print data register direct operand
JMP ADDI_END
ADDI_MODE_001: ; Invalid: An
JSR EA_INVALID ; Opcode word is Invalid
JMP ADDI_END
ADDI_MODE_010: ; (An)
JSR EA_PRINT_IND ; Print address register indirect
JMP ADDI_END ; End evaluation of ea mode
ADDI_MODE_011: ; (An)+
JSR EA_PRINT_POSTINC ; Print address register indirect with post increment
JMP ADDI_END ; End evaluation of ea mode
ADDI_MODE_100: ; -(An)
JSR EA_PRINT_PREDEC ; Print address register indirect with pre decrement
JMP ADDI_END ; End evaluation of ea mode
ADDI_MODE_101: ; Invalid: Address Register Indirect with Displacement Mode
JSR EA_INVALID ; Opcode word is Invalid
JMP ADDI_END
ADDI_MODE_110: ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JSR EA_INVALID ; Opcode word is Invalid
JMP ADDI_END
ADDI_MODE_111: ; The rest (not all valid, validated by register number)
CMP.B #$00, D7 ; Test for absolute word address
BEQ ADDI_ABS_W
CMP.B #$01, D7 ; Test for absolute long address
BEQ ADDI_ABS_L
JSR EA_INVALID ; else, invalid
JMP ADDI_END
*-----------------------------------
*--- Valid options for mode 111 ----
ADDI_ABS_W:
JSR EA_PRINT_ABS_W ; Print absolute word address operand
JMP ADDI_END
ADDI_ABS_L:
JSR EA_PRINT_ABS_L ; Print absolute long address operand
JMP ADDI_END
*-----------------------------------
ADDI_END:
JSR EA_UPDATE_POINTER ; Update global pointer
MOVEM.L (SP)+, A0-A1/A3-A5/D0-D7 ; Restore registers (except A6, global pointer to word to read)
RTS
*---------- ADDQ Effective Addresses -----------------------
* Parses and prints the effective addressing information for
* the ADDQ opcode
*-----------------------------------------------------------
EA_ADDQ:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to A5
*--- Parse data --------------------
MOVE.W (A6), D6 ; Load opcode to data register 6
MOVE.B #4, D2 ; Clear upper 4 bits of opcode word
LSL.W D2, D6 ; Perform shift (zeros shifted in)
MOVE.B #13, D2 ; 'Right-align' bits 9-11 to determine mode bits
LSR.W D2, D6 ; Perform shift (zeros shifted in)
CMP.B #$00, D6 ; Check for special case (if imm. data is 0, value is actually 8)
BNE ADDQ_PRINT_IMM ; If any value other than 0, print the data
MOVE.B #$08, D6 ; Else, the value is 0 and therefore symbolic of the value 8, so replace with the value 8
ADDQ_PRINT_IMM:
LEA POUND, A4 ; Print '#'
JSR WRITE2MEM
LEA DOLLAR, A4 ; Print '$'
JSR WRITE2MEM
MOVE.L #2, D7 ; Set size to B
JSR WRITEDATA2MEM
LEA COMMA, A4 ; Print comma
JSR WRITE2MEM
*-----------------------------------
*--- Check validity based on mode value
JSR EA_DEFAULT_COMBO
LEA ADDQ_MODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
ADDQ_MODE:
JMP ADDQ_MODE_000 ; Dn
JMP ADDQ_MODE_001 ; An
JMP ADDQ_MODE_010 ; (An)
JMP ADDQ_MODE_011 ; (An)+
JMP ADDQ_MODE_100 ; -(An)
JMP ADDQ_MODE_101 ; Invalid: Address Register Indirect with Displacement Mode
JMP ADDQ_MODE_110 ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP ADDQ_MODE_111 ; The rest (not all valid, validated by register number)
*-----------------------------------
*--- EA mode jump table options ----
ADDQ_MODE_000: ; Dn
JSR EA_PRINT_DN ; Print data register direct operand
JMP ADDQ_END ; End evaluation of ea mode
ADDQ_MODE_001: ; An
JSR EA_PRINT_AN ; Address register direct is invalid mode
JMP ADDQ_END ; End evaluation of ea mode
ADDQ_MODE_010: ; (An)
JSR EA_PRINT_IND ; Print address register indirect
JMP ADDQ_END ; End evaluation of ea mode
ADDQ_MODE_011: ; (An)+
JSR EA_PRINT_POSTINC ; Print address register indirect with post increment
JMP ADDQ_END ; End evaluation of ea mode
ADDQ_MODE_100: ; -(An)
JSR EA_PRINT_PREDEC ; Print address register indirect with pre decrement
JMP ADDQ_END ; End evaluation of ea mode
ADDQ_MODE_101: ; Invalid: Address Register Indirect with Displacement Mode
JSR EA_INVALID ; Opcode word is Invalid
JMP ADDQ_END
ADDQ_MODE_110: ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JSR EA_INVALID ; Opcode word is Invalid
JMP ADDQ_END
ADDQ_MODE_111: ; The rest (not all valid, validated by register number)
CMP.B #$00, D7 ; Test for absolute word address
BEQ ADDQ_ABS_W
CMP.B #$01, D7 ; Test for absolute long address
BEQ ADDQ_ABS_L
JSR EA_INVALID ; Opcode word is Invalid
JMP ADDQ_END
*-----------------------------------
*--- Valid options for mode 111 ----
ADDQ_ABS_W:
JSR EA_PRINT_ABS_W ; Print absolute word address operand
JMP ADDQ_END
ADDQ_ABS_L:
JSR EA_PRINT_ABS_L ; Print absolute long address operand
JMP ADDQ_END
*-----------------------------------
ADDQ_END:
JSR EA_UPDATE_POINTER ; Update global pointer
MOVEM.L (SP)+, A0-A1/A3-A5/D0-D7 ; Restore registers (except A6, global pointer to word to read)
RTS
*---------- AND Effective Addresses -------------------------
* Parses and prints the effective addressing information for
* the AND opcode
*-----------------------------------------------------------
EA_AND:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to A5
JSR EA_OPMODE_COMBO ; opmode: D6, register: D7
LEA ADD_OPMODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
*--- determine mode: mode 1 is '<ea>, Dn', mode 2 is 'Dn, <ea>'
AND_OPMODE:
JMP AND_OPMODE_000 ; mode 1, byte
JMP AND_OPMODE_001 ; mode 1, word
JMP AND_OPMODE_010 ; mode 1, long
JMP AND_OPMODE_011 ; Invalid value
JMP AND_OPMODE_100 ; mode 2, byte
JMP AND_OPMODE_101 ; mode 2, word
JMP AND_OPMODE_110 ; mode 2, long
JMP AND_OPMODE_111 ; Invalid value
*-----------------------------------
*--- Opmode jump table options -----
AND_OPMODE_000: ; mode 1, byte
MOVE.B #1, D5 ; Store size in the case of an immediate operand
JMP AND_MODE_1
AND_OPMODE_001: ; mode 1, word
MOVE.B #2, D5 ; Store size in the case of an immediate operand
JMP AND_MODE_1
AND_OPMODE_010: ; mode 1, long
MOVE.B #3, D5 ; Store size in the case of an immediate operand
JMP AND_MODE_1
AND_OPMODE_011: ; Invalid value
JSR EA_INVALID
JMP AND_END
AND_OPMODE_100: ; mode 2, byte
MOVE.B #1, D5 ; Store size in the case of an immediate operand
JMP AND_MODE_2
AND_OPMODE_101: ; mode 2, word
MOVE.B #1, D5 ; Store size in the case of an immediate operand
JMP AND_MODE_2
AND_OPMODE_110: ; mode 2, long
MOVE.B #1, D5 ; Store size in the case of an immediate operand
JMP AND_MODE_2
AND_OPMODE_111: ; Invalid value
JSR EA_INVALID
JMP AND_END
*-----------------------------------
*--- Mode 1 ------------------------
AND_MODE_1:
CLR.L D0 ; Clear data register 0
MOVE.B #1, D0 ; Save mode number to D0
MOVE.W D7, D1 ; Save register value for printing dest. operand
JSR EA_DEFAULT_COMBO ; Stores mode bits in D6, register bits in D7
JSR AND_EVAL_EA ; Evaluate the results of subroutine call
LEA COMMA, A4 ; Print comma
JSR WRITE2MEM
MOVE.W D1, D7 ; Return register value to D7 for use by subroutine
JSR EA_PRINT_DN ; Print data register
JMP AND_END
*-----------------------------------
*--- Mode 2 ------------------------
AND_MODE_2:
CLR.L D0 ; Clear data register 0
MOVE.B #2, D0 ; Save mode number to D0
JSR EA_PRINT_DN ; Print data register
LEA COMMA, A4 ; Print comma
JSR WRITE2MEM
JSR EA_DEFAULT_COMBO ; Stores mode bits in D6, register bits in D7
JSR AND_EVAL_EA ; Evaluate the results of subroutine call
JMP AND_END
*-----------------------------------
*--- Evaluate EA bits --------------
AND_EVAL_EA:
LEA AND_MODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
*--- Check validity based on mode value
AND_MODE:
JMP AND_MODE_000 ; Dn (invalid if opmode 2)
JMP AND_MODE_001 ; Invalid: An
JMP AND_MODE_010 ; (An)
JMP AND_MODE_011 ; (An)+
JMP AND_MODE_100 ; -(An)
JMP AND_MODE_101 ; Invalid: Address Register Indirect with Displacement Mode
JMP AND_MODE_110 ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP AND_MODE_111 ; The rest (not all valid, validated by register number)
*-----------------------------------
*--- EA mode jump table options ----
AND_MODE_000: ; Dn (invalid if opmode 2)
CMP #2, D0
BEQ AND_MODE_INVALID ; If opmode 2, Dn is invalid addressing mode
JSR EA_PRINT_DN ; Print data register direct operand
JMP AND_MODE_END ; End evaluation of ea mode
AND_MODE_001: ; Invalid: An
JMP AND_MODE_INVALID
AND_MODE_010: ; (An)
JSR EA_PRINT_IND ; Print address register indirect
JMP AND_MODE_END ; End evaluation of ea mode
AND_MODE_011: ; (An)+
JSR EA_PRINT_POSTINC ; Print address register indirect with post increment
JMP AND_MODE_END ; End evaluation of ea mode
AND_MODE_100: ; -(An)
JSR EA_PRINT_PREDEC ; Print address register indirect with pre decrement
JMP AND_MODE_END ; End evaluation of ea mode
AND_MODE_101: ; Invalid: Address Register Indirect with Displacement Mode
JMP AND_MODE_INVALID
AND_MODE_110: ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP AND_MODE_INVALID
AND_MODE_111: ; The rest (not all valid, validated by register number)
CMP.B #$00, D7 ; Test for absolute word address
BEQ AND_ABS_W
CMP.B #$01, D7 ; Test for absolute long address
BEQ AND_ABS_L
CMP.B #$04, D7 ; Test for immediate data
BEQ AND_IMM
JMP AND_MODE_INVALID ; else, invalid
*-----------------------------------
*--- Valid options for mode 111 ----
AND_ABS_W:
JSR EA_PRINT_ABS_W ; Print absolute word address operand
JMP AND_MODE_END
AND_ABS_L:
JSR EA_PRINT_ABS_L ; Print absolute long address operand
JMP AND_MODE_END
AND_IMM: ; invalid if opmode is 2
CMP #2, D0
BEQ AND_MODE_INVALID ; If opmode 2, An is invalid addressing mode
JSR EA_PRINT_IMM ; Print immediate data
JMP AND_MODE_END
*-----------------------------------
AND_MODE_END:
RTS ; Finish evaluating EA bits
AND_MODE_INVALID:
JSR EA_INVALID ; Opcode word is Invalid, continue to end
*-----------------------------------
AND_END:
JSR EA_UPDATE_POINTER ; Updates global pointer
MOVEM.L (SP)+, A0-A1/A3-A5/D0-D7 ; Restore registers (except A6, global pointer to word to read)
RTS
*---------- ASd Effective Addresses -------------------------
* Parses and prints the effective addressing information for
* the ASd opcode
*-----------------------------------------------------------
EA_ASd:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to A5
JSR EA_SIZE_BITS ; get size bits in D7
*--- Branch based on size bits -----
CMP.B #$03, D7 ; test if memory shift
BEQ ASd_MEM
BRA ASd_REG ; else, register shfit
*-----------------------------------
*--- Register Shift ----------------
ASd_REG:
* In preparation, isolate count/register field
MOVE.W (A6), D7 ; read opcode word in memory and save,
; (using D7 because EA_PRINT_DN uses D7)
MOVE.B #4, D2 ; Clear upper 4 bits of operand word
LSL.W D2, D7 ; Perform shift (zeros shifted in)
MOVE.B #13, D2 ; 'Right-align' bits 9-11 to get count/register field
LSR.W D2, D7 ; Perform shift (zeros shifted in)
* Isolate i/r field
MOVE.W (A6), D0 ; read opcode word in memory and save
MOVE.B #10, D2 ; Clear upper 10 bits of operand word
LSL.W D2, D0 ; Perform shift (zeros shifted in)
MOVE.B #15, D2 ; 'Right-align' bit 5 to get value
LSR.W D2, D0 ; Perform shift (zeros shifted in)
CMP.B #$00, D0 ; If i/r bit is 0, count/register field contains shift count (modulo 64)
BEQ ASd_REG_COUNT
ASd_REG_REG: ; Else, count/register field contains register number
JSR EA_PRINT_DN ; Print register value, stored in D7
JMP ASd_REG_END ; Jump to end of ASd_REG
ASd_REG_COUNT:
LEA POUND, A4 ; Print '#'
JSR WRITE2MEM
LEA DOLLAR, A4 ; Print '$'
JSR WRITE2MEM
MOVE.L #2, D7 ; Set size to B
JSR WRITEDATA2MEM *print hex value in D7 as byte todo, continue on to ASd_REG_END
ASd_REG_END:
LEA COMMA, A4 ; Print comma
JSR WRITE2MEM
JSR EA_DEFAULT_COMBO ; To get register bits in D7, 'mode' bits are not used
JSR EA_PRINT_DN ; Print register value in D7
JMP ASd_END
*-----------------------------------
*--- Memory Shift ------------------
ASd_MEM:
JSR EA_DEFAULT_COMBO ; mode: D6, register: D7
LEA ASd_MEM_MODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
*--------------------------------------
*--- Check validity based on mode value
ASd_MEM_MODE:
JMP ASd_MEM_MODE_000 ; Invalid: Dn
JMP ASd_MEM_MODE_001 ; Invalid: An
JMP ASd_MEM_MODE_010 ; (An)
JMP ASd_MEM_MODE_011 ; (An)+
JMP ASd_MEM_MODE_100 ; -(An)
JMP ASd_MEM_MODE_101 ; Invalid: Address Register Indirect with Displacement Mode
JMP ASd_MEM_MODE_110 ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP ASd_MEM_MODE_111 ; The rest (not all valid, validated by register number)
*-----------------------------------
*--- Jump table options ------------
ASd_MEM_MODE_000: ; Invalid: Dn
JSR EA_INVALID ; Data register direct is invalid mode
JMP ASd_END
ASd_MEM_MODE_001: ; Invalid: An
JSR EA_INVALID ; Address register direct is invalid mode
JMP ASd_END
ASd_MEM_MODE_010: ; (An)
JSR EA_PRINT_IND ; Print address register indirect
JMP ASd_END
ASd_MEM_MODE_011: ; (An)+
JSR EA_PRINT_POSTINC ; Print address register indirect with post increment
JMP ASd_END
ASd_MEM_MODE_100: ; -(An)
JSR EA_PRINT_PREDEC ; Print address register indirect with pre decrement
JMP ASd_END ; Continue with parsing destination operand
ASd_MEM_MODE_101: ; Invalid: Address Register Indirect with Displacement Mode
JSR EA_INVALID ; Opcode word is Invalid
JMP ASd_END
ASd_MEM_MODE_110: ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JSR EA_INVALID ; Opcode word is Invalid
JMP ASd_END
ASd_MEM_MODE_111: ; The rest (not all valid, validated by register number)
CMP.B #$00, D7 ; Test for absolute word address
BEQ ASd_MEM_ABS_W
CMP.B #$01, D7 ; Test for absolute long address
BEQ ASd_MEM_ABS_L
JSR EA_INVALID ; Else: invalid
JMP ASd_END
*-----------------------------------
*--- Valid options for mode 111 ----
ASd_MEM_ABS_W:
JSR EA_PRINT_ABS_W ; Print absolute word address operand
JMP ASd_END
ASd_MEM_ABS_L:
JSR EA_PRINT_ABS_L ; Print absolute long address operand
JMP ASd_END
*-----------------------------------
ASd_END:
JSR EA_UPDATE_POINTER ; Updates global pointer
MOVEM.L (SP)+, A0-A1/A3-A5/D0-D7 ; Restore registers (except A6, global pointer to word to read)
RTS
*---------- Bcc Effective Addresses ------------------------
* Parses and prints the effective addressing information for
* the BCC opcode
*-----------------------------------------------------------
EA_Bcc:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to A5
*--- Parse 8-bit displacement bits ----------
MOVE.W (A6), D1 ; Load opcode to data register 1
MOVE.B #8, D2 ; Clear upper 8 bits of opcode word
LSL.W D2, D1 ; Perform shift (zeros shifted in)
MOVE.B #8, D2 ; 'Right-align' bits 0-7 to determine condition
LSR.W D2, D1 ; Perform shift (zeros shifted in)
*save ultimate address to be printed
MOVEA.L A6, A4 ; Copy global pointer for dislay
CMP.B #$00, D1 ; If value is zero, real value is next word in memory
BEQ BCC_W
CMP.B #$FF, D1 ; If value is FF, real value is next longword
BEQ BCC_L
JMP BCC_B ; Else, parse lower-order byte of opcode word
*--- Sign Extension for byte displacement
BCC_B:
ADDA.L #$00000002, A4 ; Increment display pointer past opcode word
MOVE.W (A6), D3 ; Save opcode word
MOVE.B #8, D2 ; Clear upper 8 bits of opcode word
LSL.W D2, D3 ; Perform shift (zeros shifted in)
MOVE.B #15, D2 ; 'Right-align' bit 7 to determine MSB
LSR.W D2, D3 ; Perform shift (zeros shifted in)
CMP.B #$00, D3 ; If 0, sign extend with 0 (already done by isolation code)
BEQ BCC_DISPLAY
ADD.L #$FFFFFF00, D1 ; Else, sign extend data with F
JMP BCC_DISPLAY
*-----------------------------------
*--- Sign extension for word displacement
BCC_W:
ADDA.L #$00000004, A4 ; Increment display pointer past opcode word
; and displacement word in memory
ADDA.L #$00000002, A5 ; Increment A5 past opcode word
MOVE.W (A5), D3 ; Read word displacement from memory
ADDA.L #$00000002, A5 ; Increment A5 past word read
MOVE.B #15, D2 ; 'Right-align' bit 15 to determine MSB
LSR.W D2, D3 ; Perform shift (zeros shifted in)
CMP.B #$00, D3 ; If 0, sign extend with 0 (already done by isolation code)
BEQ BCC_DISPLAY
ADD.L #$FFFF0000, D1 ; Else, sign extend data with F
JMP BCC_DISPLAY
*-----------------------------------
*--- Read longword displacement ----
BCC_L:
ADDA.L #$00000006, A4 ; Increment display pointer past opcode word
; and displacement longword in memory
ADDA.L #$00000002, A5 ; Increment A5 past opcode word
MOVE.L (A5), D1 ; Read longword displacement from memory
ADDA.L #$00000004, A5 ; Increment A5 past longword read
JMP BCC_DISPLAY
*-----------------------------------
BCC_DISPLAY:
ADDA.L D1, A4 ; add displacement to current addressing
MOVE.L A4, D6 ; load address for printing
LEA TAB, A4 ; Load tab for printing
JSR WRITE2MEM
MOVE.L #8, D7 ; set size to L
JSR WRITEDATA2MEM
JSR EA_UPDATE_POINTER ; Updates global pointer
MOVEM.L (SP)+, A0-A1/A3-A5/D0-D7 ; Restore registers (except A6, global pointer to word to read)
RTS
*---------- CLR Effective Addresses ------------------------
* Parses and prints the effective addressing information for
* the CLR opcode
*-----------------------------------------------------------
EA_CLR:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to ASd
JSR EA_DEFAULT_COMBO ; mode: D6, register: D7
LEA CLR_MODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
*--------------------------------------
*--- Check validity based on mode value
CLR_MODE:
JMP CLR_MODE_000 ; Dn
JMP CLR_MODE_001 ; Invalid: An
JMP CLR_MODE_010 ; (An)
JMP CLR_MODE_011 ; (An)+
JMP CLR_MODE_100 ; -(An)
JMP CLR_MODE_101 ; Invalid: Address Register Indirect with Displacement Mode
JMP CLR_MODE_110 ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP CLR_MODE_111 ; The rest (not all valid, validated by register number)
*-----------------------------------
*--- Jump table options ------------
CLR_MODE_000: ; Dn
JSR EA_PRINT_DN
JMP CLR_END
CLR_MODE_001: ; Invalid: An
JSR EA_INVALID ; Address register direct is invalid mode
JMP CLR_END
CLR_MODE_010: ; (An)
JSR EA_PRINT_IND ; Print address register indirect
JMP CLR_END
CLR_MODE_011: ; (An)+
JSR EA_PRINT_POSTINC ; Print address register indirect with post increment
JMP CLR_END
CLR_MODE_100: ; -(An)
JSR EA_PRINT_PREDEC ; Print address register indirect with pre decrement
JMP CLR_END ; Continue with parsing destination operand
CLR_MODE_101: ; Invalid: Address Register Indirect with Displacement Mode
JSR EA_INVALID ; Opcode word is Invalid
JMP CLR_END
CLR_MODE_110: ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JSR EA_INVALID ; Opcode word is Invalid
JMP CLR_END
CLR_MODE_111: ; The rest (not all valid, validated by register number)
CMP.B #$00, D7 ; Test for absolute word address
BEQ CLR_ABS_W
CMP.B #$01, D7 ; Test for absolute long address
BEQ CLR_ABS_L
JSR EA_INVALID ; Else: invalid
JMP CLR_END
*-----------------------------------
*--- Valid options for mode 111 ----
CLR_ABS_W:
JSR EA_PRINT_ABS_W ; Print absolute word address operand
JMP CLR_END
CLR_ABS_L:
JSR EA_PRINT_ABS_L ; Print absolute long address operand
JMP CLR_END
*-----------------------------------
CLR_END:
JSR EA_UPDATE_POINTER ; Updates global pointer
MOVEM.L (SP)+, A0-A1/A3-A5/D0-D7 ; Restore registers (except A6, global pointer to word to read)
RTS
*---------- CMP Effective Addresses ------------------------
* Parses and prints the effective addressing information for
* the CMP opcode
*-----------------------------------------------------------
EA_CMP:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to A5
*--- Check validity based on mode value
JSR EA_DEFAULT_COMBO
LEA CMP_MODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
CMP_MODE:
JMP CMP_MODE_000 ; Dn
JMP CMP_MODE_001 ; An
JMP CMP_MODE_010 ; (An)
JMP CMP_MODE_011 ; (An)+
JMP CMP_MODE_100 ; -(An)
JMP CMP_MODE_101 ; Invalid: Address Register Indirect with Displacement Mode
JMP CMP_MODE_110 ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP CMP_MODE_111 ; The rest (not all valid, validated by register number)
*-----------------------------------
*--- EA mode jump table options ----
CMP_MODE_000: ; Dn
JSR EA_PRINT_DN ; Print data register direct operand
JMP CMP_MODE_END ; End evaluation of ea mode
CMP_MODE_001: ; An
JSR EA_PRINT_AN ; Address register direct is invalid mode
JMP CMP_MODE_END ; End evaluation of ea mode
CMP_MODE_010: ; (An)
JSR EA_PRINT_IND ; Print address register indirect
JMP CMP_MODE_END ; End evaluation of ea mode
CMP_MODE_011: ; (An)+
JSR EA_PRINT_POSTINC ; Print address register indirect with post increment
JMP CMP_MODE_END ; End evaluation of ea mode
CMP_MODE_100: ; -(An)
JSR EA_PRINT_PREDEC ; Print address register indirect with pre decrement
JMP CMP_MODE_END ; End evaluation of ea mode
CMP_MODE_101: ; Invalid: Address Register Indirect with Displacement Mode
JSR EA_INVALID ; Opcode word is Invalid
JMP CMP_END
CMP_MODE_110: ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JSR EA_INVALID ; Opcode word is Invalid
JMP CMP_END
CMP_MODE_111: ; The rest (not all valid, validated by register number)
CMP.B #$00, D7 ; Test for absolute word address
BEQ CMP_ABS_W
CMP.B #$01, D7 ; Test for absolute long address
BEQ CMP_ABS_L
CMP.B #$04, D7 ; Test for immediate data
BEQ CMP_IMM
JSR EA_INVALID ; Opcode word is Invalid
JMP CMP_END
*-----------------------------------
*--- Valid options for mode 111 ----
CMP_ABS_W:
JSR EA_PRINT_ABS_W ; Print absolute word address operand
JMP CMP_MODE_END
CMP_ABS_L:
JSR EA_PRINT_ABS_L ; Print absolute long address operand
JMP CMP_MODE_END
CMP_IMM:
JSR EA_OPMODE_COMBO ; get opmode bits in D6, register bits not used
MOVE.B D6, D5 ; Set (size - 1)
ADD.B #1, D5 ; Set size
JSR EA_PRINT_IMM ; Print immediate data
JMP CMP_MODE_END
*-----------------------------------
*--- Evaluate and print register ---
CMP_MODE_END:
LEA COMMA, A4 ; Print comma
JSR WRITE2MEM
JSR EA_OPMODE_COMBO ; get register bits in D7, opmode bits not used
JSR EA_PRINT_DN ; print register
CMP_END:
JSR EA_UPDATE_POINTER ; Update global pointer
MOVEM.L (SP)+, A0-A1/A3-A5/D0-D7 ; Restore registers (except A6, global pointer to word to read)
RTS
*---------- DIVU.W Effective Addresses -----------------------
* Parses and prints the effective addressing information for
* the DIVU.W opcode
*-----------------------------------------------------------
EA_DIVU_W:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to A5
JSR EA_DEFAULT_COMBO ; mode: D6, register: D7
LEA DIVU_W_MODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
*--- Check validity based on mode value
DIVU_W_MODE:
JMP DIVU_W_MODE_000 ; Dn
JMP DIVU_W_MODE_001 ; Invalid: An
JMP DIVU_W_MODE_010 ; (An)
JMP DIVU_W_MODE_011 ; (An)+
JMP DIVU_W_MODE_100 ; -(An)
JMP DIVU_W_MODE_101 ; Invalid: Address Register Indirect with Displacement Mode
JMP DIVU_W_MODE_110 ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP DIVU_W_MODE_111 ; The rest (not all valid, validated by register number)
*-----------------------------------
*--- Jump table options ------------
DIVU_W_MODE_000: ; Dn
JSR EA_PRINT_DN ; Print data register direct operand
JMP DIVU_W_DEST ; Go to: print destination operand
DIVU_W_MODE_001: ; Invalid: An
JSR EA_INVALID ; Address register direct is invalid mode
JMP DIVU_W_END
DIVU_W_MODE_010: ; (An)
JSR EA_PRINT_IND ; Print address register indirect
JMP DIVU_W_DEST
DIVU_W_MODE_011: ; (An)+
JSR EA_PRINT_POSTINC ; Print address register indirect with post increment
JMP DIVU_W_DEST
DIVU_W_MODE_100: ; -(An)
JSR EA_PRINT_PREDEC ; Print address register indirect with pre decrement
JMP DIVU_W_DEST ; Continue with parsing destination operand
DIVU_W_MODE_101: ; Invalid: Address Register Indirect with Displacement Mode
JSR EA_INVALID ; Opcode word is Invalid
JMP DIVU_W_END
DIVU_W_MODE_110: ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JSR EA_INVALID ; Opcode word is Invalid
JMP DIVU_W_END
DIVU_W_MODE_111: ; The rest (not all valid, validated by register number)
CMP.B #$00, D7 ; Test for absolute word address
BEQ DIVU_W_ABS_W
CMP.B #$01, D7 ; Test for absolute long address
BEQ DIVU_W_ABS_L
CMP.B #$04, D7 ; Test for immediate data
BEQ DIVU_W_IMM
JSR EA_INVALID ; Else: invalid
JMP DIVU_W_END
*-----------------------------------
*--- Valid options for mode 111 ----
DIVU_W_ABS_W:
JSR EA_PRINT_ABS_W ; Print absolute word address operand
JMP DIVU_W_DEST ; Continue with parsing destination operand
DIVU_W_ABS_L:
JSR EA_PRINT_ABS_L ; Print absolute long address operand
JMP DIVU_W_DEST ; Continue with parsing destination operand
DIVU_W_IMM:
MOVE.B #2, D5 ; Size is word
JSR EA_PRINT_IMM ; Print immediate data
JMP DIVU_W_DEST ; Continue with parsing destination operand
*-----------------------------------
DIVU_W_DEST:
LEA COMMA, A4 ; Print comma
JSR WRITE2MEM
*Get destination register
MOVE.W (A6), D7 ; Load word at current pointer to D1
MOVE.B #4, D2 ; Clear upper 4 bits of opcode word
LSL.W D2, D7 ; Perform shift (zeros shifted in)
MOVE.B #13, D2 ; 'Right-align' bits 9-11 to determine register
LSR.W D2, D7 ; Perform shift (zeros shifted in)
JSR EA_PRINT_DN ; Print data register direct operand
DIVU_W_END:
JSR EA_UPDATE_POINTER ; Update global pointer
MOVEM.L (SP)+, A0-A1/A3-A5/D0-D7 ; Restore registers (except A6, global pointer to word to read)
RTS
*---------- JSR Effective Addresses ------------------------
* Parses and prints the effective addressing information for
* the JSR opcode
*-----------------------------------------------------------
EA_JSR:
MOVEM.L A0-A1/A3-A5/D0-D7, -(SP) ; Save registers (except A6, global pointer to word to read)
JSR EA_COPY_PTR ; Copy global pointer to ASd
JSR EA_DEFAULT_COMBO ; mode: D6, register: D7
LEA JSR_MODE, A0 ; Set index '0' for jump table
MULU #6, D6 ; Form offset (move 6 bytes in memory for every 'JMP' command)
JMP 0(A0, D6) ; Jump indirect with index, i.e. jump to 'table' + displacement
*--------------------------------------
*--- Check validity based on mode value
JSR_MODE:
JMP JSR_MODE_000 ; Invalid: Dn
JMP JSR_MODE_001 ; Invalid: An
JMP JSR_MODE_010 ; (An)
JMP JSR_MODE_011 ; Invalid: (An)+
JMP JSR_MODE_100 ; Invalid: -(An)
JMP JSR_MODE_101 ; Invalid: Address Register Indirect with Displacement Mode
JMP JSR_MODE_110 ; Invalid: Address Register Indirect with Index (8-Bit Displacement)
JMP JSR_MODE_111 ; The rest (not all valid, validated by register number)
*-----------------------------------
*--- Jump table options ------------
JSR_MODE_000: ; Invalid: Dn
JSR EA_INVALID ; Data register direct is invalid mode