Opcode fetch machine cycle of 8085 :
Each instruction of the processor has one byte opcode.
The opcodes are stored in memory. So, the processor executes the opcode fetch machine cycle to fetch the opcode from memory.
Hence, every instruction starts with opcode fetch machine cycle.
The time taken by the processor to execute the opcode fetch cycle is 4T.
In this time, the first, 3 T-states are used for fetching the opcode from memory and the remaining T-states are used for internal operations by the processor.
Memory Read Machine Cycle of 8085:
The memory read machine cycle is executed by the processor to read a data byte from memory.
The processor takes 3T states to execute this cycle.
The instructions which have more than one byte word size will use the machine cycle after the opcode fetch machine cycle.
Fig - Timing Diagram for Opcode Fetch Machine Cycle
Fig - Timing Diagram for Memory Read Machine Cycle
Timing Diagram of Machine cycles...(Contd) - >>Page2