i8254

Macros
#define	TIMER_FREQ   1193182
	clock frequency for timer in PC and AT
#define	BIT(n)   (0x01<<(n))
#define	TIMER0_IRQ   0
	Timer 0 IRQ line.
#define	TIMER_0   0x40
	Timer 0 count register.
#define	TIMER_1   0x41
	Timer 1 count register.
#define	TIMER_2   0x42
	Timer 2 count register.
#define	TIMER_CTRL   0x43
	Control register.
#define	SPEAKER_CTRL   0x61
	Register for speaker control.
#define	TIMER_SEL0   0x00
	Control Word for Timer 0.
#define	TIMER_SEL1   BIT(6)
	Control Word for Timer 1.
#define	TIMER_SEL2   BIT(7)
	Control Word for Timer 2.
#define	TIMER_RB_CMD   (BIT(7)|BIT(6))
	Read Back Command.
#define	TIMER_LSB   BIT(4)
	Initialize Counter LSB only.
#define	TIMER_MSB   BIT(5)
	Initialize Counter MSB only.
#define	TIMER_LSB_MSB   (TIMER_LSB | TIMER_MSB)
	Initialize LSB first and MSB afterwards.
#define	TIMER_SQR_WAVE   (BIT(2)|BIT(1))
	Mode 3: square wave generator.
#define	TIMER_RATE_GEN   BIT(2)
	Mode 2: rate generator.
#define	TIMER_BCD   0x01
	Count in BCD.
#define	TIMER_BIN   0x00
	Count in binary.
#define	TIMER_RB_COUNT_   BIT(5)
#define	TIMER_RB_STATUS_   BIT(4)
#define	TIMER_RB_SEL(n)   BIT((n)+1)

Detailed Description

Constants for programming the i8254 Timer. Needs to be completed.