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The MOS Technology 6502 is an example of a microprocessor using a PLA for instruction decode and sequencing. The PLA is visible in photomicrographs of the chip, [12] and its operation can be seen in the transistor-level simulation. Microprogramming is still used in modern CPU designs.
The types of operations may include arithmetic, data copying, logical operations, and program control, as well as special instructions (e.g., CPUID). [10] In addition to the opcode, many instructions also specify the data (known as operands) the operation will act upon, although some instructions may have implicit operands or none at all. [10]
Machine code is generally different from bytecode (also known as p-code), which is either executed by an interpreter or itself compiled into machine code for faster (direct) execution. An exception is when a processor is designed to use a particular bytecode directly as its machine code, such as is the case with Java processors .
Based on the source code written for μC/OS, and introduced as a commercial product in 1998, μC/OS-II is a portable, ROM-able, scalable, preemptive, real-time, deterministic, multitasking kernel for microprocessors, and digital signal processors (DSPs). It manages up to 64 tasks.
Minimal instruction set computer (MISC) is a central processing unit (CPU) architecture, usually in the form of a microprocessor, with a very small number of basic operations and corresponding opcodes, together forming an instruction set. Such sets are commonly stack-based rather than register-based to reduce the size of operand specifiers.
The Motorola 6800 microprocessor was the first for which an undocumented assembly mnemonic HCF became widely known. The operation codes (opcodes—the portions of the machine language instructions that specify an operation to be performed) hexadecimal 9D and DD were reported and given the unofficial mnemonic HCF in a December 1977 article by Gerry Wheeler in BYTE magazine on undocumented ...
Decoding the op-code in the instruction register includes determining the instruction, determining where its operands are in memory, retrieving the operands from memory, allocating processor resources to execute the command (in super scalar processors), etc.
One-operand operations on memory same as 13-bit, plus CNEQSN 0: 1: 0: 1: 1: 1: 1: address: CNEQSN addr — C: Z: Compute A − [addr], then skip if non-zero 0 1 1 opc bit ioaddr Bit operations with I/O same as 13-bit, but 64-byte range 1 0 0 opc bit address Bit operations with memory same as 13-bit, but 64-byte range 1 0 1 opcode literal ...