3. 8085 addressing modes
Download as PPTX, PDF0 likes311 views
This document discusses different addressing modes of the 8085 microprocessor instruction set, including: 1) Direct addressing where the operand address is specified in the instruction. 2) Register addressing where the operand is in a general purpose register specified by the opcode. 3) Register indirect addressing where the operand address is specified by a register pair like H-L. 4) Immediate addressing where the operand is specified within the instruction. 5) Implicit addressing where certain instructions like CMA operate directly on the accumulator without an explicit operand address.
3. 8085 addressing modes
- 1. MICROPROCESSOR 8085 LECTURE 6 INSTRUCTION SET-ADDRESSING MODES PROF. SANDIP DAS
- 2. ADDRESSING MODES Direct Addressing: In this Addressing mode the address of the operand is given in the instruction itself. Examples: STA 2400 (32,00,24)-Stores the content of accumulator in address 2400H LDA 0034 (3A,3A,00)- Loads the accumulator with the content of address 003AH OPCODE ADDRESS ADDRESS 00000000 10000000 00110010 00111100 00000000 01110110 Main Memory Direct Addressing Mode Instruction Format
- 3. REGISTER ADDRESSING In this addressing mode the operand is in one of the general purpose registers. The opcode specifies the address of the register(s) in addition to the operation performed. Examples are: MOV A,B Content of register B is moved to register A • Opcode for the above instruction is 78H. • In binary form 78H is written as 01111000. • The first two bits i.e. 01 are for MOV operation, the next three bits 111 are for register A and last three bits 000 are for register B. ADD B Add the content of register B to the content of register A • Opcode for the above instruction is 80H • Here one operand is register B as mentioned and the other operand is Accumulator (for arithmetic operation, it is understood). The opcode 80H is written as 10000000. • The first five bits i.e., 10000, specify the add operation to e performed and
- 4. REGISTER INDIRECT ADDRESSING In this addressing the address of the operand is specified by a register pair. Example 1: LXI H,2500 Load H-L pair with 2500H MOV A,M Move the content of the memory location, whose address is in H- L pair HLT Example 2: LXI H,2500 Load H-L pair with 2500H ADD M ADD the content of the memory location, whose address is in H-L pair with A HLT
- 5. IMMEDIATE ADDRESSING In immediate addressing mode the operand is specified within the instruction itself. Examples 1: MVI A,05 Move 05 in Accumulator 3E, 05 Opcode for the above instruction Examples 2: ADI A,16 ADD 16 to the content of Accumulator C6, 16 Opcode for the above instruction LXI is also an example of immediate addressing.
- 6. IMPLICIT ADDRESSING Certain instruction which operate on the content of the accumulator. Such instructions do not require address of the operand. Examples: CMA Complement the accumulator RLC Rotate accumulator left RRC Rotate accumulator right RAL Rotate accumulator left through carry RAR Rotate accumulator right through carry
- 7. ASSIGNMENT-1 MARKS-10 1. Draw the timing diagram of MOV A,B. How many T-states and machine cycle will this operation require. 2. Draw the timing diagram of ADD B. How many T-states and machine cycle will this operation require. SUBMISSION DATE: 30/07/2018