instructionclassificationandaddressingmode-全文預(yù)覽
【正文】 H AX 。 1 implied SRC, 1 implied DEST Instruction Classification (2) 1) Transfer instruction 2) Arithmetic instruction 3) Bit Manipulation instruction 4) String instruction 5) Program transfer instruction 6) Processor control instruction Addressing Mode Addressing mode means how CPU obtain the operation data in instructions. (1) Register Addressing (2) Immediate Addressing (3) Memory Addressing (4) String Addressing (5) I/O Port Addressing Addressing Mode Addressing Mode is a concept for operation data, not for instruction. If there are two operation data in an instruction, there may be two different addressing modes. Example: MOV AX, VAR1 DEST: Register Addressing SRC: Memory Addressing (1) Register Addressing If operation data is in CPU register, the addressing mode is register addressing. Example: mov al, bl DEST: Register addressing SRC: Register addressing (1) Register Addressing Because no bus operation needed in register addressing, it is the fastest addressing mode of CPU. (2) Immediate Addressing If the operation data is immediate data in instructions, the addressing mode is immediate addressing. Example: mov al, 02h DEST: Register Addressing SRC: Immediate Addressing (2) Immediate Addressing Because immediate data is part of instruction, it will be loaded to instruction queue in instruction reading cycle (not execution cycle). Bus operation is needed for reading data. However, because EU and BIU can work synchronously, the time consumed in immediate data reading can be ignored in some situations. Memory Addressing When operation data is in memory, the addressing mode is memory addressing. Bus operation is needed in this addressi
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