Functions
int	timer_set_frequency (unsigned char timer, unsigned long freq)
	Changes the operating frequency of a timer. More...

int	timer_subscribe_int (void)
	Subscribes and enables Timer 0 interrupts. More...

int	timer_unsubscribe_int ()
	Unsubscribes Timer 0 interrupts. More...

void	timer_int_handler ()
	Timer 0 interrupt handler. More...

int	timer_get_conf (unsigned char timer, unsigned char *st)
	Reads the input timer configuration via read-back command. More...

int	timer_display_conf (unsigned char conf)
	Shows timer configuration. More...

int	timer_test_time_base (unsigned long freq)
	Tests change of Timer O interrupt frequency. More...

int	timer_test_int (unsigned long time)
	Tests Timer 0 interrupt handling. More...

int	timer_test_config (unsigned char timer)
	Tests display of timer config. More...

Detailed Description

Functions for using the i8254 timers

Function Documentation

◆ timer_display_conf()

int timer_display_conf ( unsigned char conf )

Shows timer configuration.

Displays in a human friendly way, the configuration of a timer as read via the read-back command, by providing the values (and meanings) of the different components of a timer configuration

Parameters

conf	configuration to display in human friendly way

Returns: Return 0 upon success and non-zero otherwise

◆ timer_get_conf()

int timer_get_conf	(	unsigned char	timer,
		unsigned char *	st
	)

Reads the input timer configuration via read-back command.

Parameters

timer	Timer whose config to read (Ranges from 0 to 2)
st	Address of memory position to be filled with the timer config

Returns: Return 0 upon success and non-zero otherwise

◆ timer_int_handler()

void timer_int_handler ( )

Timer 0 interrupt handler.

Increments counter

◆ timer_set_frequency()

int timer_set_frequency	(	unsigned char	timer,
		unsigned long	freq
	)

Changes the operating frequency of a timer.

Must not change the 3 LSBs (mode and BCD/binary) of the timer's control word.

Parameters

timer	Timer to configure. (Ranges from 0 to 2)
freq	Timer operating frequency

Returns: Return 0 upon success and non-zero otherwise

◆ timer_subscribe_int()

int timer_subscribe_int ( void )

Subscribes and enables Timer 0 interrupts.

Returns: Returns bit order in interrupt mask; negative value on failure

◆ timer_test_config()

int timer_test_config ( unsigned char timer )

Tests display of timer config.

Just calls timer_get_conf() followed by timer_display_conf()

Parameters

timer Timer whose config to read (Ranges from 0 to 2)

Returns: Return 0 upon success and non-zero otherwise

◆ timer_test_int()

int timer_test_int ( unsigned long time )

Tests Timer 0 interrupt handling.

Subscribes Timer 0 interrupts and prints a message once per second for the specified time interval

Parameters

time	Length of time interval while interrupts are subscribed

Returns: Return 0 upon success and non-zero otherwise

◆ timer_test_time_base()

int timer_test_time_base ( unsigned long freq )

Tests change of Timer O interrupt frequency.

Programs Timer 0 to generate interrupts with input frequency

Parameters

freq	Frequency of interrupts to generate

Returns: Return 0 upon success and non-zero otherwise

◆ timer_unsubscribe_int()

int timer_unsubscribe_int ( )

Unsubscribes Timer 0 interrupts.

Returns: Return 0 upon success and non-zero otherwise