Understanding ARM9E Instruction Cycle Timings

ARM9E Instruction Cycle Timings

The ARM9E core is one of the most popular cores used in a range of embedded applications and is based on the classic ARMv5 architecture. It operates at a maximum frequency of 200 MHz and typically needs four instruction cycles to execute an instruction. This article will provide an overview of ARM9E instruction cycle timings, including key definitions and parameters.

Definition of Instruction Cycles

Instruction cycles refer to the number of clock cycles it takes for the ARM9E processor to complete an instruction. An instruction can be broken down into three stages, which are:

• Instruction fetch - This is where the instruction is fetched from memory and stored in the instruction register.
• Instruction decode - The decoder then reads the instruction and determines what action should be taken.
• Instruction execution - The arithmetic logic unit (ALU) then carries out the instructions.

These three stages together form one instruction cycle. Therefore, if the ARM9E takes four instruction cycles to complete an instruction, it will take twelve clock cycles total.

Key Parameters

Along with instruction cycle times, there are a number of other parameters that need to be considered when analyzing ARM9E instruction cycle timings. These include instruction pipeline length, branch prediction accuracy, available instruction widths and more.

The instruction pipeline length refers to the maximum number of instructions that can be processed in parallel. With the ARM9E, this is typically 4-stages for single-threaded operations. Branch prediction accuracy is also important, as it measures the probability that a branch instruction will take the predicted path. For the ARM9E, branch prediction accuracy is usually around 85%.

Available instruction widths determine how wide the processor can handle instructions. The ARM9E supports up to five instruction widths, ranging from 16-bits to 64-bits. Finally, there is the issue of temporal locality, which refers to how much data can be reused when executing multiple instructions. Since the ARM9E is optimized for low-power operation, temporal locality is usually quite high.

Conclusion

In conclusion, the ARM9E processor is one of the most popular core architectures available and is optimized for low-power operation using an instruction pipeline length of four-stages. It typically requires 4 instruction cycles for one instruction and has branch prediction accuracy of around 85%. Available instruction widths range from 16-bits to 64-bits and temporal locality is usually quite high.