Anonymous user
Interrupts: Difference between revisions
Jump to navigation
Jump to search
m
→From the keyboard's perspective
| [unchecked revision] | [unchecked revision] |
m (Better wording) |
|||
Line 17:
Basically, when a key is pressed, the keyboard controller tells a device called the [[PIC|Programmable Interrupt Controller]], or PIC, to cause an interrupt. Because of the wiring of keyboard and PIC, IRQ #1 is the keyboard interrupt, so when a key is pressed, IRQ 1 is sent to the PIC. The role of the PIC will be to decide whether the CPU should be immediately notified of that IRQ or not and to translate the IRQ number into an ''interrupt vector'' (i.e. a number between 0 and 255) for the CPU's table.
The OS is supposed to handle the interrupt by talking to the keyboard, via <tt>in</tt> and <tt>out</tt> instructions (or <tt>inportb</tt>/<tt>outportb</tt>, <tt>inportw</tt>/<tt>outportw</tt>, and <tt>inportd</tt>/<tt>outportd</tt> in C, see [[Inline Assembly/Examples]]), asking what key was pressed, doing something about it (such as displaying the key on the screen, and notifying the current application that a key has been pressed), and returning to whatever code was executing when the interrupt came in. Indeed, failure to read the key from the buffer will prevent any subsequent IQRs from the keyboard.
==From the PIC's perspective==
| |||