Opcode in a sentence

For example, using AL as an accumulator and adding an immediate byte value to it produces the efficient add to AL opcode of 04h, whilst using the BL register produces the generic and longer add to register opcode of 80C3h.

Generally, a mnemonic is a symbolic name for a single executable machine language instruction (an opcode ), and there is at least one opcode mnemonic defined for each machine language instruction.

In addition to the opcode, R-type instructions specify three registers, a shift amount field, and a function field; I-type instructions specify two registers and a 16-bit immediate value; J-type instructions follow the opcode with a 26-bit jump target.

The binary is then modified using the debugger or a hex editor or monitor in a manner that replaces a prior branching opcode with its complement or a NOP opcode so the key branch will either always execute a specific subroutine or skip over it.

A 7-bit function field follows, which is used in conjunction with the opcode to specify an operation.

A complete machine language instruction consists of an opcode and, in many cases, additional bits that specify arguments for the operation (for example, the numbers to be summed in the case of an addition operation).

All these CPUs are opcode compatible (including undocumented opcodes ).

As an example, the opcode 26h followed by an immediate byte value (LD H,n) will load that value into the H register.

Assembly language instructions usually consist of an opcode mnemonic followed by a list of data, arguments or parameters. citation These are translated by an assembler into machine language instructions that can be loaded into memory and executed.

Branch instructions have a 6-bit opcode field, a 5-bit Ra field and a 21-bit displacement field.

Due to the regular encoding of the MOV instruction (using a quarter of available opcode space), there are redundant codes to copy a register into itself (MOV B,B, for instance), which were of little use, except for delays.

For example, "SMA SZA", opcode 7540, skips if AC ≤ 0. A Group 2 OPR instruction that has none of the microprogrammed bits set is another No-Op instruction.

However, as they are not part of the formal definition of the instruction set, different implementations of the Z80 are not guaranteed to work the same way for every undocumented opcode.

However the address of the opcode typically cannot contain any null characters and the locations of these opcodes can vary between applications and versions of the operating system.

In assembly language, these options were specified by adding a letter to the opcode: 'L' — shift left; 'R' — shift right, 'S' — swap bytes; nothing — do not perform a shift or swap.

In assembly language, these options were specified by adding a letter to the opcode: 'O' — set the carry bit; 'Z' — clear the carry bit, 'C' — complement the carry bit, nothing — leave the carry bit alone.

In assembly language, the signal was specified by adding a letter to the opcode: 'S' for start, 'C' for clear, 'P' for pulse, and nothing for no signal.

Instruction set Instructions are all 1 to 3 bytes long, consisting of an initial opcode byte, followed by up to 2 bytes of operands.

It contains a 6-bit opcode field, followed by the Ra field, which specifies the register containing the first operand and the Rb field, specifies the register containing the second operand.

It was never formally a part of the PowerPC architecture until this specification although it used PowerPC instruction formats and syntax and occupied the opcode space expressly allocated for such purposes.