Question:
Write a step by step execution of things that happen after a user presses a key on the keyboard. Use as much detail as possible.
Answer:
1. The keyboard sends a scan code of the key to the keyboard controller (Scan code for key pressed and key released is different).
2. The keyboard controller interprets the scan code and stores it in a buffer.
3. The keyboard controller sends a hardware interrupt to the processor. This is done by putting signal on “interrupt request line”: IRQ 1.
4. The interrupt controller maps IRQ 1 into INT 9.
5. An interrupt is a signal which tells the processor to stop what it was doing currently and do some special task.
6. The processor invokes the “Interrupt handler”. CPU fetches the address of “Interrupt Service Routine” (ISR) from “Interrupt Vector Table” maintained by the OS (Processor use the IRQ number for this).
7. The ISR reads the scan code from port 60h and decides whether to process it or pass the control to program for taking action.
-
Explain There is not interrupt PIN for PCIe interrupt. When device wants to raise an interrupt, an interrupt message is sent to host via ... -
Configure Space Addressing One of the major improvements the PCI Local Bus had over other I/O architectures was its configuration mechanism... -
What is LMA and VMA Every loadable or allocatable output section has two addresses. The first is the VMA, or virtual memory address. This ...
No comments:
Post a Comment