Is my flowchart for programmed io and interrput drive io correct?

[shivajikobardan]

Source of my knowledge-: https://electronics.stackexchange.com/questions/204337/programmed-io-vs-interrupt-for-devices

https://slideplayer.com/slide/265620/



And my teacher.



So here is what I understand about



1) Programmed IO-:

 Here CPU periodically executes instruction which reads READY pin



2) Interrupt driven IO-:

Here CPU checks interrupt at the end of each instruction cycle whereas IO device sends interrupt.

The original flowchart for these are as follows-:

https://imgur.com/a/fIwwxyf

Here is what I have made-:



https://imgur.com/a/0woBT73

First one is programmed io and second one is interrupt driven io. In interrupt driven io I mistakenly drew arrow from "CPU issues read command to IO module" to "hardware/CPU checks for interrupt at the end of each instruction cycle".


I just want to know if my understanding of flowchart is correct or not?

[westfw]

I would say that in Programmed IO, the SOFTWARE issues a read command to the IO device and checks the ready pin, while with interrupts the CPU Hardware checks for interrupt after each instruction.  And I don't like that in the original diagram ends the interrupt by going to the top, instead of with a "return from interrupt" - I would draw the whole "interrupt" routine as disconnected from the main program flowchart.  (but that doesn't agree with your textbook, so it might not be the answer that they want.)