Determining Instruction Cycle Length and Interrupt Acknowledgement Delay
Microprocessor Instruction Cycle and Interrupt Handling
Questions:
a. Determine the length of the instruction cycle for the case of a string of 64 bytes. b. What is the worst-case delay for acknowledging an interrupt if the instruction is non-interruptible? c. Repeat part (b) assuming the instruction can be interrupted at the beginning of each byte transfer.Answers:
a. The length of the instruction cycle for a string of 64 bytes is 970 clock cycles. b. The worst-case delay for acknowledging an interrupt is 0.06467 microseconds if the instruction is non-interruptible. c. If the instruction can be interrupted at the beginning of each byte transfer, the worst-case delay for acknowledging an interrupt is 970 clock cycles. Explanation:
a. The length of the instruction cycle can be calculated by adding the clock cycles for fetching and initial decoding, and the clock cycles for transferring each byte. For a string of 64 bytes, the instruction cycle would be 10 + (64 * 15) = 970 clock cycles.
b. The worst-case delay for acknowledging an interrupt if the instruction is non-interruptible would be the length of the instruction cycle divided by the clock rate. In this case, it would be 970 / 15 GHz = 0.06467 microseconds.
c. If the instruction can be interrupted at the beginning of each byte transfer, the worst-case delay for acknowledging an interrupt would be the same as part (a), which is 970 clock cycles, since the interrupt can occur after each byte transfer begins.