#include "devices/pit.h"#include <debug.h>#include <stdint.h>#include "threads/interrupt.h"#include "threads/io.h"
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Macros | |
| #define | PIT_PORT_CONTROL 0x43 |
| Interface to 8254 Programmable Interrupt Timer (PIT). More... | |
| #define | PIT_PORT_COUNTER(CHANNEL) (0x40 + (CHANNEL)) |
| Counter port. More... | |
| #define | PIT_HZ 1193180 |
| PIT cycles per second. More... | |
Functions | |
| void | pit_configure_channel (int channel, int mode, int frequency) |
| Configure the given CHANNEL in the PIT. More... | |
Macro Definition Documentation
◆ PIT_HZ
◆ PIT_PORT_CONTROL
| #define PIT_PORT_CONTROL 0x43 |
◆ PIT_PORT_COUNTER
| #define PIT_PORT_COUNTER | ( | CHANNEL | ) | (0x40 + (CHANNEL)) |
Function Documentation
◆ pit_configure_channel()
| void pit_configure_channel | ( | int | channel, |
| int | mode, | ||
| int | frequency | ||
| ) |
Configure the given CHANNEL in the PIT.
In a PC, the PIT's three output channels are hooked up like this:
- Channel 0 is connected to interrupt line 0, so that it can be used as a periodic timer interrupt, as implemented in Pintos in devices/timer.c.
- Channel 1 is used for dynamic RAM refresh (in older PCs). No good can come of messing with this.
- Channel 2 is connected to the PC speaker, so that it can be used to play a tone, as implemented in Pintos in devices/speaker.c.
MODE specifies the form of output:
- Mode 2 is a periodic pulse: the channel's output is 1 for most of the period, but drops to 0 briefly toward the end of the period. This is useful for hooking up to an interrupt controller to generate a periodic interrupt.
- Mode 3 is a square wave: for the first half of the period it is 1, for the second half it is 0. This is useful for generating a tone on a speaker.
- Other modes are less useful.
FREQUENCY is the number of periods per second, in Hz.
Definition at line 46 of file pit.c.
References ASSERT, intr_disable(), intr_set_level(), mode, outb(), PIT_HZ, PIT_PORT_CONTROL, and PIT_PORT_COUNTER.
Referenced by speaker_on(), and timer_init().
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