Programmable Interval Timer

Functions

void pit_init(void);

void pit_set_divisor(uint16_t divisor);

void pit_set_frequency(freq_hz_t freq_hz);

void pit_set_interval_ns(time_ns_t interval_ns);

void pit_set_periodic_mode(uint16_t divisor);

void pit_set_oneshot_mode(uint16_t divisor);

void pit_wire_periodic_nmi(time_ns_t interval_ns);

freq_hz_t pit_measure_tsc_freq(void);

#define PIT_PORT_CHANNEL0 0x40

#define PIT_PORT_CHANNEL1 0x41

#define PIT_PORT_CHANNEL2 0x42

#define PIT_PORT_COMMAND 0x43

#define PIT_PORT_CHANNEL(ch) ((uint16_t) (PIT_PORT_CHANNEL0 + (ch)))

#define PIT_BASE_FREQUENCY_HZ 1193182ULL

#define PIT_FREQUENCY 1193182ULL

#define PIT_CMD_CHANNEL(ch) ((uint8_t) (((ch) & 0x3) << 6))

#define PIT_CMD_CHANNEL0 0x00

#define PIT_CMD_CHANNEL1 0x40

#define PIT_CMD_CHANNEL2 0x80

#define PIT_CMD_READBACK 0xC0

#define PIT_CMD_ACCESS_LATCH 0x00 /* Latch count value command */

#define PIT_CMD_ACCESS_LO 0x10    /* Low byte only */

#define PIT_CMD_ACCESS_HI 0x20    /* High byte only */

#define PIT_CMD_ACCESS_LOHI 0x30  /* Low byte then high byte (16 bit) */

#define PIT_CMD_MODE_ONESHOT 0x00

#define PIT_CMD_MODE_HW_ONESHOT 0x02

#define PIT_CMD_MODE_RATE_GEN 0x04

#define PIT_CMD_MODE_SQUARE_WAVE 0x06

#define PIT_CMD_MODE_SW_STROBE 0x08

#define PIT_CMD_MODE_HW_STROBE 0x0A

#define PIT_CMD_BINARY 0x00

#define PIT_CMD_BCD 0x01

#define PIT_DEFAULT_MODE 0x34

#define PIT_DEFAULT_COUNT 0x4AF2

#define PIT_CALIBRATION_MODE 0x30

#define PIT_CALIBRATION_COUNT UINT16_MAX

#define PIT_DIVISOR_MIN 1

#define PIT_DIVISOR_MAX_COUNT UINT16_MAX

#define PIT_DIVISOR_ROLLOVER_VAL 0 /* 0 is 65536 in binary mode */