"Assembly language" learning Note 2--Register

8086 Registers

CPU has 14 registers: AX, BX, CX, DX, SI, DI, SP, BP, IP, CS, SS, DS, ES, PSW

1. Universal register (Data Register): AX, BX, CX, DX. For storing general data

AX: Used as an accumulator, is the primary register of arithmetic operators

BX: Base Register

CX: Counters

DX: Used to store a double-byte operand with ax when doing double-precision operations

2. Address register: Pointer, variable address register. (SI, DI, SP, BP)

SI: Source address register, which holds the offset address of the source buffer

DI: The destination register, which holds the offset address of the destination buffer

SP: Stack pointer register to indicate the offset address of the stack area

BP: Base point pointer Register to indicate the offset address of the stack to a cell

3. Segment register: CS, DS, ES, SS

CS: Code segment register, which indicates the segment address of the code snippet that holds the program

DS: Data segment register, which indicates the segment address of the data segment where the data is stored

ES: Additional segment registers that indicate the segment address of additional segments that hold additional data

SS: Stack register, which indicates the segment address of the stack segment to which the stack is going

4. Control register: IP, FLAGS (PSW program status word). Implementation of control procedures

IP: Instruction register, which holds the offset address of the code snippet, indicates the offset address of the unit where the next instruction is currently executing the instruction

A 16-bit register can store a 16-bit data (that is, the data maximum value is 2 of 16 square minus 1,65535)

These can be divided into two 8-bit registers: H, L. The suffix h is a high 8-bit register (AH) and L is a low 8-bit register (AL)

A 8-bit register data with a maximum of 2 8-time minus 1,255

8086CPU can handle two sizes of data at once:

Byte (byte): A byte consists of 8 bits (bit) (that is, bits), which can exist in a 8-bit register

Word: One word consists of two bytes, two bytes for the word's high and low bytes, respectively

CPU features for 16-bit architectures:

1. The operator handles up to 16 bits of data at a time

2. The maximum width of the register is 16 bits

3. The path between the register and the operator is 16 bits

"Assembly language" learning Note 2--Register