This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Example of instructions, doesn't use functional unit at all?

Hello to all,

I need a small help with the processor instructions. Can anybody provide me an example where during execution, the functional unit must not be used or it must be deactivated? 

All data-processing and data-transfer instruction need the functional unit. Initially, I thought the NOP instruction can be one of the examples, but while going through the documentations, I got to know that NOP instruction is nothing but the MOV R8,R8. 

I really want to measure the effect of functional unit activation and deactivation. So, is there any instruction example or any measurement technique, which will be helpful in our case?

I am working on ARM Cortex-M4.

Thanking you in advance,

Warm Regards,

Himanshu

Parents
  • Dear Mr. Yiu,

    Thank you very much for your quick reply. But while implementing the MOV R8,R8 was displayed as the nop instruction in the assembly. Therefore, I got confused. 

      (this assembly file has been generated for Cortex-M4 for LPCXpresso 54114 board)

    But, when I implemented the only "NOP" instruction, (not in any other instruction form) directly, then I got to know the assembly of NOP is different. (As shown in the  attached picture)

    So, in my case, is it okay to consider the NOP instruction as an instruction, which does not use the functional unit or deactivates the functional unit??

    Because, as seen in the uploaded picture the first line of instruction is MOV R8,R8 has been also shown as the NOP instruction. And we know that the MOV instruction uses the functional unit. 

    So, is it okay to use the NOP instruction directly??...If not then which instruction shall I use, which won't use the functional unit. 

     Sorry for posting the wrong remarks earlier. Since I got confused with the assembly stuff.

    Thanking you once again for your proper guidance,

    Kind Regards,

    Himanshu

Reply
  • Dear Mr. Yiu,

    Thank you very much for your quick reply. But while implementing the MOV R8,R8 was displayed as the nop instruction in the assembly. Therefore, I got confused. 

      (this assembly file has been generated for Cortex-M4 for LPCXpresso 54114 board)

    But, when I implemented the only "NOP" instruction, (not in any other instruction form) directly, then I got to know the assembly of NOP is different. (As shown in the  attached picture)

    So, in my case, is it okay to consider the NOP instruction as an instruction, which does not use the functional unit or deactivates the functional unit??

    Because, as seen in the uploaded picture the first line of instruction is MOV R8,R8 has been also shown as the NOP instruction. And we know that the MOV instruction uses the functional unit. 

    So, is it okay to use the NOP instruction directly??...If not then which instruction shall I use, which won't use the functional unit. 

     Sorry for posting the wrong remarks earlier. Since I got confused with the assembly stuff.

    Thanking you once again for your proper guidance,

    Kind Regards,

    Himanshu

Children