Addressing Modes in 8051
- Instructions operate on data
- Data can be the value itself or in CPU register or in internal memory or in external memory
- Addressing mode refers to how you are accessing the data
- Addressing modes are in integral part of each computer’s instruction set
- There are 8 addressing mode determines how the operand byte is selected: Register, Direct, Indirect, Immediate, Relative, Absolute, Long, Indexed
- Register: Data is in Registers
- Direct: Data is in on-chip RAM
- Indirect: Data is in memory but its location is computed during run time
- Immediate: Data is a value which is stored immediately next to opcode in memory
- Relative: Data is a relative address (8-bits) to which the program control has to be transferred
- Absolute: Data is an absolute address (11-bits) to which the program control has to be transferred
- Long: Data is an address (16-bits) location where the program branches
- Indexed: Data, elements of look-up table entries, located in the program ROM space of the 8051
| Addressing Modes | Instruction |
|---|---|
| Register | MOV A, B |
| Direct | MOV 30H, A |
| Indirect | ADD A, @R0 |
| Immediate | ADD A,#80H |
| Relative | SJMP +127/-128 of PC |
| Absolute | AJMP within 2K |
| Long | LJMP FAR |
| Indexed | MOVC A,@A+PC |
Related topics:
8051 Register Addressing Mode | 8051 Direct Addressing Mode | 8051 Indirect Addressing Mode | 8051 Immediate Addressing Mode | 8051 Relative Addressing Mode | 8051 Absolute Addressing Mode | 8051 Long Addressing Mode | 8051 Indexed Addressing Mode | 8051 External Addressing Mode
List of topics: 8051
No comments:
Post a Comment