There is a communication channel between IOP and CPU to perform task which come under computer architecture. This channel explains the commands executed by IOP and CPU while performing dome programs. The CPU do not executes the instructions but it assigns the task of initiating operations, the instructions are executed by IOP. I/O transfer is instructed by CPU. The IOP asks for CPU through interrupt.
This channel starts by CPU, by giving “test IOP path” instruction to IOP and then the communication begins as shown in diagram:
Whenever CPU gets interrupt from IOP to access memory, it sends test path instruction to IOP. IOP executes and check for status, if the status given to CPU is OK, then CPU gives start instruction to IOP and gives it some control and get back to some another (or same) program, after that IOP is able to access memory for its program.
Now IOP start controlling I/O transfer using DMA and create another status report as well. AS soon as this I/O transfer completes IOP once again send interrupt to CPU, CPU again request for status of IOP, IOP check status word from memory location and gives it to CPU. Now CPU check the correctness of status and continues with the same process.
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