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Monday, May 20, 2013

Instruction set of 8085

Instruction set is a collection of instructions that a processor can execute. Microprocessor operates on these instructions. If an instruction that is not in the instruction set of a particular microprocessor, is invalid for that processor. Each instruction in 8085 belongs to a particular group depending upon the task they perform. These Instructions are classified as:

1) Data Transfer Group: These Instructions are used to transfer data from one register to another, memory to register or from register to memory. E.g. MOV, MVI, STA, LXI, LDA, LHLD, SHLD, LDAX, STAX, XCHG etc.

2) Arithmetic Group: These instructions are used to perform arithmetic operations such as addition, subtraction, Increment, Decrement etc. ADD, INR, SUB, DAA are some examples of Arithmetic Group instruction set of 8085.

3) Logical Group: These Instruction are used to perform logical operations such as AND, OR comparison, rotate etc. ANA, ANI, ORA, ORI, XRA, CMP, CPI, RLC, RRC, RAL, RAR are some examples of logical group instructions.

4) Branch Control Group: These types of instruction are used by 8085 for conditional or conditional jumps, calling or return subroutines etc. JMP, JC, JZ, RST, CALL are some examples of Branch control group instructions.

5) Machine and I/O Control Group: This Instruction group contains instructions for I/O ports, Stack and Machine control.IN, OUT, PUSH, POP, HLT, XTHL, SPHL, EI, DI, SIM, RIM, NOP are some examples of Machine and I/O Control Group.

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