1 Contents: 3.1 Instruction format and Addressing Modes 3.2 Instruction Introduction Chapter 3 Instruction system

2 Assemble Language: symbolic language Assembler: A computer program used to assemble Source Program  Assembler  Object program （ Source codes ） （ Machine codes ） Instruction Set: can not transplant directly Chapter 3 Instruction system 3.1 Instruction format and Addressing Modes

Instruction format Instruction = opcode operand = opcode destination operand, source operand Instruction types: 1-byte Instruction: includes opcode and operand 2-byte Instruction: 1th byte is opcode 2th byte is operand 3-byte Instruction: 1th byte is opcode 2th, 3th byte are operands

4 3.1 Instruction format and Addressing Modes Addressing: how to get the location of (source) operand. Addressing Modes: 7 types 1. Register Addressing 2. Direct Addressing 3. Register Indirect Addressing 4. Immediate Constants Addressing 5. Indexed Addressing 6. Boolean Addressing Addressing Modes 7. Relative Addressing （ get the jumping destination address of PC ）

Addressing Modes 1. Register Addressing Operand: denoted by register. For example: MOV A, R0 Addressing Range: ① General register: 4 banks × 8 （ R0 ～ R7 ）＝ 32 registers ② Some SFRs: A, AB, DPTR, etc.

Addressing Modes Operand: denoted directly by 8-bit address. For example: MOV A, 3AH Addressing Range: ① Lower 128 bytes of internal RAM ② SFRs 2. Direct Addressing

Addressing Modes Operand: specifies a register to contain operand address with the prefix ”. Addressing Range: ① Lower 128 bytes of internal RAM （ 8-bit address ） ② 64KB of external RAM （ 16-bit address ） 3. Register Indirect Addressing address register of 8-bit address: Ri （ i = 0, 1 ） SP （ PUSH, POP ） address register of 16-bit address: DPTR For example: MOV R0 MOVX

Addressing Modes Operand: specifies the value of a 8-bit or 16-bit constant with the prefix “ # ”. For example: MOV A, #3AH MOV DPTR, # 0200H 4. Immediate Constants Addressing

Addressing Modes Only three instruction: MOVC MOVC Addressing Range: Program Memory （ ROM ） 5. Indexed Addressing Program Memory can only be accessed via this mode. Designed for reading look-up tables in Program Memory or executing unconditional jumps. A 16-bit base register （ DPTR or PC ） points to the base address of table, and A is set up with the table entry number. The 16-bit address in ROM is formed by adding the A data to the base pointer.

Addressing Modes Addressing Range: 1. Bit addressable area in Internal RAM cell address: 20H~2FH, bit address: 00H~7FH  2 ways to specifies the addressing bit: ① Cell address + bit: 20H.6 ② Bit address: 06H 6. Boolean Addressing 2. Addressable bit in SFRs  4 ways to specifies the addressing bit ① SFR symbol + bit: PSW.5 ② Bit address: 0D5H ③ Cell address + bit: 0D0H.5 ④ Bit name: F0

Addressing Modes offset Range: （ backward ） ~ （ forward ） 7. Relative Addressing Used for getting the jumping destination address of PC in Jump Instruction. Destination address = PC + rel PC = （ address + byte number ） of Jump instruction rel = 8-bit relative offset byte Return