Enum Instruction

pub enum Instruction {
    CLS,
    RET,
    JMP(JmpData),
    CALL(CallData),
    SKIP(SkipData),
    MOV(MovData),
    ADD(AddData),
    OR(OrData),
    AND(AndData),
    XOR(XorData),
    SUB(SubData),
    SHR(ShrData),
    SUBN(SubnData),
    SHL(ShlData),
    JPC(JpcData),
    RAND(RandData),
    DRAW(DrawData),
    GDL(GdlData),
    KEY(KeyData),
    SDL(SdlData),
    SND(SndData),
    SCH(SchData),
    BCD(BcdData),
    RDP(RdpData),
    RLD(RldData),
}

A Chip-8 instruction. All instructions that execute a calculation store the result in their first argument.

Variants

CLS

Clears the screen

RET

Returns from a subroutine

JMP(JmpData)

Unconditionally jumps to an address

CALL(CallData)

Calls a subroutine

SKIP(SkipData)

Skips the next instruction if a SkipType condition is met

MOV(MovData)

Assigns values to registers or moves one register’s value into another

ADD(AddData)

Adds two registers, or a register and a value. When both operands are registers, VF is set to 1 when the result exceeds the size of the destination register, and 0 otherwise.

OR(OrData)

Bitwise ORs two registers

AND(AndData)

Bitwise ANDs two registers

XOR(XorData)

Bitwise XORs two registers

SUB(SubData)

Subtracts one register from another, with the second register subtracted from the first. VF is set to 0 when there’s a borrow, and 1 if there isn’t.

SHR(ShrData)

Stores the least significant bit of a register in VF and shifts that register to the right 1 bit

SUBN(SubnData)

Subtracts one register from another, with the first register subtracted from the second. VF is set to 0 when there’s a borrow, and 1 when there isn’t.

SHL(ShlData)

Stores the most significant bit of a register in VF and shifts that register to the left one bit

JPC(JpcData)

Unconditionally jumps to an address defined by a constant plus the V0 register

RAND(RandData)

Stores a random 8-bit integer bitwise ANDed with a given constant in a register

DRAW(DrawData)

Draws a sprite at coordinates defined by two registers with a width of 8 pixels and a given height. The sprite is read as bits from memory starting at address I. VF is set to 1 if any pixels are flipped from on to off, and to 0 if not.

GDL(GdlData)

Sets a register to the current value of the delay timer

KEY(KeyData)

Stops execution until a key is pressed, then stores that key in a register

SDL(SdlData)

Sets the delay timer to the value of a register

SND(SndData)

Sets the sound timer to the value of a register

SCH(SchData)

Puts the memory location of the hex character corresponding to the value of a register into I

BCD(BcdData)

Stores the binary-coded decimal representation of a register in memory location I, with the hundreds digit in the lowest byte.

RDP(RdpData)

Dumps the contents of all registers up to and including a specified register into memory starting at location I

RLD(RldData)

Loads all registers up to and including a specified register from data starting at location I