The ARM processor follows the Von-Neuman Execution strategy. In this strategy, the scientist followed the load-store architecture i.e, the instruction first store in the memory and execute sequentially.
ARM Instruction Execution
The execution Process of ARM instruction execution cycle is 4 phase:-
- Fetch:- In this phase, the processor fetches the instruction from memory.
- Decode:- In this second fetch, the processor decodes the instruction as per the opcode given in the instruction.
- Advance:- In the next phase, advance phase the processor updates the program counter that is PC=PC+1.
- the processor run in word addressability the PC incremented with ‘1’.
- it is byte addressability PC=PC+4.
- Execution:- The last phase is the execution phase. In this phase, the instruction is executed by ALU operation.
ARM processor uses a clocking scheme to perform different operations. It uses a 2 phase clock which is a non-overlapping in nature to perform the search operation. For this, it uses level-sensitive latch is a circuit that is level trigger output can change it differs from flipflop, flipflop is an age triggered that is only it changes that is low to high and high to low.
The ARM processor uses the latches to avoid rest condition, Rest condition happens when the multiple instructions an executed in an overlapping time frame. To avoid this condition ARM processor use 2 phase non-overlapping term.
The ARM processor can be programmed by using assembly language programming. The assembly language programming used assembly instruction to perform the task. The assembly instruction is written by using especially symbol known as memory.
The assembly instruction is divided into 4 parts:-
OPCODE:- The opcode is used for different types of operation. That operation may be arithmetic or logical operations.
LEVEL:- Level is used when there is a loop in the program this can be written by PPQQXX etc.
OPERAND:- It consists of the operand itself or the address of the operand to be used with the opcode. The operand may be a registered address or a memory address or any value which can be made operational with the operation code.
COMMENT:- Comments are used to make the program easy to understand . These lines are started with a semi control.