Understanding 8085 Microprocessor Instruction Size | FAQs

[mkbh_10]

How does the Microprocessor(8085) know the size of an instruction ?

 

[zeitghost]

The instruction decode logic is designed so that multibyte instructions result in further byte fetches from memory.

 

[oswaler]

The 8085 microprocessor has a built-in instruction decoder that is responsible for interpreting and executing instructions. This decoder uses a pre-determined instruction set architecture, which specifies the size and format of each instruction. Therefore, the microprocessor knows the size of an instruction based on the instruction set architecture it is designed with.

In the case of the 8085 microprocessor, the instruction size is determined by the number of bytes required to represent the instruction. This can range from 1 to 3 bytes, depending on the complexity of the instruction. The first byte of an instruction is always the opcode, which tells the microprocessor what operation to perform. The subsequent bytes, if any, provide additional information or operands for the instruction.

The size of an instruction is also determined by the addressing mode used. The 8085 microprocessor supports different addressing modes such as immediate, direct, indirect, and indexed addressing. Each of these modes requires a different number of bytes to represent the instruction.

In summary, the microprocessor knows the size of an instruction through the instruction set architecture and the addressing mode used. This information is crucial for the proper execution of instructions and is a fundamental aspect of understanding the functioning of the 8085 microprocessor.