As mentioned in my earlier posts, the i/p instructions are fed to i/p unit. To know about it in details, refer . Now, lets discuss about how Signal transmission happens to CPU. During the commencement of an instruction cycle, the Central Processing Unit collects each and every i/p instructions from the i/p unit and put it in the reprogrammable memory in the form of a ‘Process image’. It is therefore, this reprogrammable memory is also known as Process Image Input (PII).

Input of Process control

As soon as the Central processing unit completes the storing of i/p instructions to PII, the program starts to execute layer by layer. Depending upon the program instructions, the Central processing unit then carry out logical/arithmetic functions from Process Image Input. It also calculates the timing and counting provided by timer/counter and understands/provides flag-states for indication purpose. What is a Flag-state?? It is just a binary representation in ‘1’ and ‘0’ which indicates a particular condition.

Input of Process control phase two

The calculation result is then put again in the registers ( CPU’s internal memory). The internal-memory is also known as Process Output Image (PIQ). After this operation, the Central processing unit then move the data from PIQ to the O/p component. Accordingly, the o/p unit then controls actual o/p mechanism. Thus, the signal transmission chain is finally completed.

 Output of Process control system