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Clock Manager
[Kernel]

Data Structures
struct	timeout
	Timeout variable structure. More...
Defines
#define	LATCH_COUNT   0x00
	To copy chip count.
#define	TIMER0   0x40
	I/O port for timer channel 0.
#define	TIMER2   0x42
	I/O port for timer channel 2.
#define	TIMER_MODE   0x43
	I/O port for timer mode control.
#define	SQUARE_WAVE   0x36
	The sqare-wave form.
#define	TIMER_FREQ   1193182L
	Clock frequency for timer in PC.
#define	TIMER_COUNT   (unsigned)(TIMER_FREQ/HZ)
	Value to initialize timer.
#define	LATCH   ((TIMER_FREQ + HZ/2) / HZ)
	LATCH is used for the interval timer.
#define	HZ   200
	Clock Frequancy (User settable, default=200Hz).
#define	usleep(m)   delay(m)
	Macro equivalent to delay(dword millisec).
Typedefs
typedef timeout	timeout_t
	Timeout variable structure.
Functions
void	init_clock ()
	Initialize channel 0 of the 8253A timer.
void	stop_clock ()
	Reset the clock for rebooting.
dword	sys_get_ticks (void)
	Return the system ticks. Returns: The system ticks.
void	delay (dword millisec)
	Delay some milliseconds Parameters: millisec  How many milliseconds you want to delay.
void	set_timeout (timeout_t *t, unsigned int millisec)
	Initialize a timeout variable. Parameters: t  The timeout variable. millisec  How many milliseconds have to elapse before the timeout occurs.
bool	is_timeout (timeout_t *t)
	Check if a timeout has been elapsed. Parameters: t  The timeout variable.
void	clock_thread ()
	This is a task that occurs at every clock tick.

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Detailed Description

The system clock manager.

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Define Documentation

#define HZ   200

Clock Frequancy (User settable, default=200Hz). Definition at line 31 of file clock.h.

#define LATCH   ((TIMER_FREQ + HZ/2) / HZ)

LATCH is used for the interval timer. Definition at line 28 of file clock.h.

#define LATCH_COUNT   0x00

To copy chip count. Definition at line 17 of file clock.h.

#define SQUARE_WAVE   0x36

The sqare-wave form. Definition at line 21 of file clock.h.

#define TIMER0   0x40

I/O port for timer channel 0. Definition at line 18 of file clock.h.

#define TIMER2   0x42

I/O port for timer channel 2. Definition at line 19 of file clock.h.

#define TIMER_COUNT   (unsigned)(TIMER_FREQ/HZ)

Value to initialize timer. Definition at line 25 of file clock.h.

#define TIMER_FREQ   1193182L

Clock frequency for timer in PC. Definition at line 22 of file clock.h.

#define TIMER_MODE   0x43

I/O port for timer mode control. Definition at line 20 of file clock.h.

#define usleep (  m    )     delay(m)

Macro equivalent to delay(dword millisec). Definition at line 48 of file clock.h.

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Typedef Documentation

typedef struct timeout timeout_t

Timeout variable structure.

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Function Documentation

void clock_thread (    )

This is a task that occurs at every clock tick. Into this routine you can put every periodical task. You can change the frequency of the ticks changing the value of the HZ definition. This thread is invoked at every clock tick by the dispatcher(). Definition at line 109 of file clock.c. { ticks++; floppy_thread(); }

void delay (  dword    millisec )

Delay some milliseconds Parameters: millisec  How many milliseconds you want to delay. Definition at line 51 of file clock.c. { dword count, elapsed; dword IF = GET_IF(); // Start timer // elapsed = 0; while (elapsed < millisec) { // Poll ticks in memory // count = ticks; // Auto-sleep // enable(); idle(); // Update elapsed time // elapsed += (ticks - count)*1000/HZ; } SET_IF(IF); }

void init_clock (    )

Initialize channel 0 of the 8253A timer. Definition at line 21 of file clock.c. { dword IF = GET_IF(); disable(); outportb(TIMER_MODE, SQUARE_WAVE); // set timer on outportb(TIMER0, TIMER_COUNT & 0xFF); // timer low byte outportb(TIMER0, TIMER_COUNT >> 8); // timer high byte SET_IF(IF); }

bool is_timeout (  timeout_t *    t )

Check if a timeout has been elapsed. Parameters: t  The timeout variable. Definition at line 87 of file clock.c. { // Check if a timeout has gone // uint32_t elapsed; elapsed = ticks - t->start_ticks; return( elapsed >= t->ticks_to_wait ); }

void set_timeout (  timeout_t *    t, unsigned int    millisec )

Initialize a timeout variable. Parameters: t  The timeout variable. millisec  How many milliseconds have to elapse before the timeout occurs. Definition at line 79 of file clock.c. { t->start_ticks = ticks; t->ticks_to_wait = millisec * HZ / 1000; }

void stop_clock (    )

Reset the clock for rebooting. Definition at line 35 of file clock.c. { dword IF = GET_IF(); disable(); outportb(TIMER_MODE, SQUARE_WAVE); // set timer on outportb(TIMER0, 0); // timer low byte outportb(TIMER0, 0); // timer high byte SET_IF(IF); }

dword sys_get_ticks (  void    )

Return the system ticks. Returns: The system ticks. Definition at line 97 of file clock.c. { return(ticks); }

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