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sd:appendix_4_instruction_set_architecture [2026/04/14 06:09] – external edit (Unknown date) 127.0.0.1sd:appendix_4_instruction_set_architecture [2026/04/23 04:14] (current) – appledog
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-= Appendix 4 Instruction Set Architecture +[[ISA]]
- +
-=== Load/Store Instructions +
-^ Byte ^ Code ^ Example ^ Description | +
-| 00 | LD_IMM   | LDA $5         | Load register with immediate value | +
-| 01 | LD_MEM   | LDA [$5]       | Load register from memory location | +
-| 02 | LD_REG   | LDA [X]        | load register from memory location | +
-| 03 | LD_REG24 | LDA [X:Y]      | Load register from memory location using [low_byte:word] | +
-| 04 | LD_IMM24 | LDA [$1:$C000] | Load byte from memory location [bank:addr] | +
-| 05 | ST_MEM   | STA [$10]      | Store register in memory location | +
-| 06 | ST_REG   | STA [X]        | Store A in memory location using register as pointer | +
-| 07 | ST_REG24 | STA [X:Y]      | Store A in memory using [low_byte:word] registers. | +
-| 08 | ST_IMM24 | STA [$0:$A0]   | Store register in memory location [bank:addr] | +
- +
-<codify armasm> +
-; ld/st example +
-    LDA $1234        ; Load immediate $1234 into A +
-    LDAL $42         ; Load immediate byte $42 into AL +
-    LDA  [$F000]     ; Load word from address $F000 +
-    STA [2:$1000]    ; Store A to bank 2, offset $1000 +
-    STA [B:X]        ; Store into bank BL, offset X. +
-    STA [BLX]        ; Store into bank BL, offset X. +
-</codify> +
- +
-==== Assembly +
-    00            LD_REG +
-    00            A +
-    01 02         $201 (little endian) +
- +
-=== Data Movement Instructions of the Caribbean +
-^ Byte ^ Code ^ Example ^ Description | +
-| 09   | MOV        | MOV Y, A                    | Copy A up on Y | +
-| 0A   | XCHG       | XCHG X, Y                   | Swap dem two -- X an Y trade place, quick quick | +
- +
-==== Assembly +
-    09 00 01          MOV A, B +
-    0A 02 03          XCHG X, Y +
- +
-=== Pirate Stack Operations +
-^ Byte ^ Code ^ Example ^ Description | +
-| 0B   | PUSH       | PUSH A                      | Push A onto stack -- ye scurvy dog! | +
-| 0C   | POP        | POP Y                       | Pull stack value an' hand it over to register | +
-| 0D   | PUSHA      | PUSHA                       | Save all registers in ye treasure chest | +
-| 0E   | POPA       | POPA                        | Get the registers back | +
-| 0F   | PUSHF      | PUSHF                       | Push "pirate" flags/status | +
-| 10   | POPF       | POPF                        | Pop "pirate" flags back | +
- +
-=== Boring, Normal increment operations +
-|= Byte |= Code              |= Example              |= Description +
-| 15   | INC                | INC X                 | Increment register by 1 (any size: byte/word/etc.) +
-| 16   | DEC                | DEC Y                 | Decrement register by 1 (any size) +
- +
-=== Arithmetic Operations +
-| 1E   | ADD                | ADD X, Y              | Add X = X + Y | +
-| 1F   | SUB                | SUB X, Y              | Subtract X = X - Y | +
-| 20   | MUL                | MUL X, Y              | Multiply X:Y = X * Y \\ //(result may be 32-bit wide)// | +
-| 21   | DIV                | DIV X, Y              | Divide X = X / Y **//and Y = X % Y (for free)//** +
-| 22   | MOD                | MOD X, Y              | Modulo X = X % Y +
-| 23   | ADD_REG_IMM        | ADD X, $1234          | Add immediate word value; X = X + immediate +
-| 24   | SUB_REG_IMM        | SUB X, $ABCD          | Subtract immediate; X = X - immediate +
-| 25   | MUL_REG_IMM        | MUL X, $100           | Multiply by immediate; X:Y = X * immediate +
-| 26   | DIV_REG_IMM        | DIV X, $10            | Divide by immediate; X = quotient, Y = remainder +
-| 27   | MOD_REG_IMM        | MOD X, $FF            | Modulo by immediate; X = X % immediate +
-| 28   | ADDC               | ADDC X, Y             | Add with carry; X = X + Y + carry flag +
-| 29   | SUBC               | SUBC X, Y             | Subtract with borrow; X = X - Y - borrow +
-| 30   | ADDC_REG_IMM       | ADDC X, $5            | Add imm w/carry; X = X + imm + carry +
-| 31   | SUBC_REG_IMM       | SUBC X, $1            | Subtract w/carry X = X - imm - borrow +
- +
- +
-=== Logic Ops +
-|= Byte |= Instruction |= Example |= Description |= Flags Affected | +
-| 32   | AND                | AND dst, src          | Bitwise AND (compare two integers bit by bit) | | +
-| 33   | OR                 | OR dst, src           | Bitwise OR (same) | | +
-| 34   | XOR                | OR dst, src           | Bitwise XOR | | +
-| 35   | NOT                | NOT reg               | Invert all bits in an integer word | | +
-| 36   | TEST               | TEST dst, src         | Non-destructive AND | | +
-| 37   | AND_IMM            | AND dst, imm          | Bitwise AND with immediate | | +
-| 38   | OR_IMM             | OR dst, imm           | Bitwise OR with immediate | | +
- +
-=== Shift/Rotate Operations +
-|= Byte |= Instruction |= Example |= Description |= Flags Affected | +
-| 46   | SHL  | SHL A     | Shift left   | Z, N, C | +
-| 47   | SHR  | SHR A     | Shift right  | Z, N, C | +
-| 48   | SHLC | SHLC A    | Shift left   | Z, N, C | +
-| 49   | SHRC | SHRC A    | Shift right  | Z, N, C | +
-| 4A   | ROL  | ROL A     | Rotate left  | Z, N, C | +
-| 4B   | ROR  | ROR A     | Rotate right | Z, N, C | +
-| 4C   | ROLC | ROLC A    | Rotate left  | Z, N, C | +
-| 4D   | RORC | RORC A    | Rotate right | Z, N, C | +
- +
-=== Comparison & Branching +
-|= Byte |= Instruction |= Example |= Description |= Flags Affected | +
-| 5A | CMP     | CMP A, B      | Compare (subtract, discard result) | Z, N, C, V | +
-| 5B | CMP_IMM | CMP A, 0x0001 | Compare (subtract, discard result) | Z, N, C, V | +
- +
-| | JMP | | Unconditional jump  | None | +
-| | JZ  | | Jump if zero        | None | +
-| | JNZ | | Jump if not zero    | None | +
-| | JC  | | Jump if carry set   | None | +
-| | JNC | | Jump if carry clear | None | +
- +
-=== Subroutine Operations +
-|= Byte |= Instruction |= Example |= Description |= Flags Affected | +
-| | CALL | | Call subroutine (push IP, jump) | | +
-| | RET  | | Return from subroutine (pop IP) | | +
-| | INT  | | Software interrupt | | +
-| | RTI  | | Return from Interrupt | | +
- +
-=== MMU/Block Operations +
-| 8C | MEMCOPY  | MEMCOPY ELM, FLD, I | Copy memory from ptr to ptr. | | +
-| 8D | SCAN  | SCAN H, N | Scan ptr H for needle N | | +
-| 8E | CMPC3 | CMPC3 ELM, FLD, C | Compare Characters | Z C | +
-| 8F | SKPC | SKPC ELM, AL | Skip characters | | +
-| 90 | SKPC_IMM | SKPC ELM, $20 | Skip characters (immediate) | | +
- +
-These instructions are mainly inspired by instructions on the VAX architecture. +
- +
-* ''MEMCOPY'' -- The VAX has ''MOVC3'' and ''MOVC5'' instructions. +
-* ''SCAN'' -- The VAX has ''SCANC'' and ''LOCC'' instructions. +
-* ''CMPC3'' -- //Compare Characters// is a VAX instruction; ''CMPC3'' and ''CMPC5''. +
-* ''SKPC'' -- //Skip Character// is a VAX instruction. +
- +
-The VAX was indeed ahead of it's time. This is not surprising as it was the most successful Super-Minicomputer of it's time. In the later microcomputer era, the 680x0 brought over a lot of functionality, but remained more RISC like, requiring tight loops to replicate instructions like the above. +
- +
-=== Bit Packing +
-| 98 | PAB | PAB | Pack low 4 bytes of A and low 4 bytes of B into AL | | +
-| 99 | UAB | UAB | Unpack AL into low 4 bytes of AL and low 4 bytes of BL | | +
- +
- +
-=== Flag Operations +
-|= Byte |= Instruction |= Example |= Description |= Flags Affected | +
-| A0 | SEZ     | SEZ | Set zero flag | Z | +
-| A1 | SEN     | SEN | Set negative flag | N | +
-| A2 | SEC     | SEC | Set carry flag | C | +
-| A3 | SEV     | | Set overflow flag | V | +
-| A4 | SEE     | | Set Extra Flag (User flag) | E | +
-| A5 | SEF     | | Set Free Flag (User flag) | F | +
-| A6 | SEB     | | Set Bonus Flag (User flag) | B | +
-| A7 | SEU     | | Set User Flag (User flag) | U | +
-| A8 | SED     | | Set Debug Flag | D | +
-| A9 | SEI     | | Set Enable Interrupt | I | +
-| AA | SSI     | | Enable Sound System Interrupts | S | +
-| AB | CLZ     | | Clear zero flag | Z | +
-| AC | CLN     | | Clear negative flag | N | +
-| AD | CLC     | | Clear carry flag | C | +
-| AE | CLV     | | Clear overflow flag | V | +
-| AF | CLE     | CLE | Clear E | E | +
-| B0 | CLF     | CLF | Clear F Flag (user flag)  | F | +
-| B1 | CLB     |     | | B | +
-| B2 | CLU     |     | | U | +
-| B3 | CLD     |     | | D | +
-| B4 | CLI     | CLI | Clear Interrupt Flag | I | +
-| B5 | CSI     | CSI | Clear Sound Interrupt  | S | +
-| B6 | SETF    | SETF 0x80     | Set bits in flags | * | +
-| B7 | CLRF    | CLRF 0x80     | Clear bits in flags | * | +
-| B8 | TESTF   | TESTF 0x80    | Non-destructive AND | Z C | +
- +
-=== Other +
-|= Instruction |= Description | +
-| TSX | Transfer SP to register* | +
-| TXS | Transfer register to SP* | +
- +
-* (*) these opcodes were suggested by stackminer from the Fantasy Console 2.0 discord. Thank you, stackminer! +
- +
-=== System Operations +
-|= Instruction |= Description | +
-| YIELD | Poll UI, System Clock, Sound Chip, Video Chip, and others | +
-| NOP | No operation | +
-| HALT | Halt CPU (set H flag) | +
sd/appendix_4_instruction_set_architecture.1776146946.txt.gz · Last modified: by 127.0.0.1
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