1 /*

2 Copyright 2004 John Tsiombikas <nuclear@siggraph.org>

3

4 This file is part of libgba, a library for GameBoy Advance development.

5

6 This program is free software; you can redistribute it and/or modify

7 it under the terms of the GNU General Public License as published by

8 the Free Software Foundation; either version 2 of the License, or

9 (at your option) any later version.

10

11 This program is distributed in the hope that it will be useful,

12 but WITHOUT ANY WARRANTY; without even the implied warranty of

13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

14 GNU General Public License for more details.

15

16 You should have received a copy of the GNU General Public License

17 along with this program; if not, write to the Free Software

18 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

19 */

20

21 #include <limits.h>

22 #include "intr.h"

23 #include "signal.h"

24

25 /* prescalar selection based on the system clock (16.78MHz) */

26 #define TIMER_CNTL_CLK 0

27 #define TIMER_CNTL_CLK64 1

28 #define TIMER_CNTL_CLK256 2

29 #define TIMER_CNTL_CLK1024 3

30

31 /* control bits */

32 #define TIMER_CNTL_COUNTUP 4

33 #define TIMER_CNTL_INTR 0x40

34 #define TIMER_CNTL_ENABLE 0x80

35

36 static void timer_intr_handler(void);

37

38 volatile static unsigned short *reg_timer[] = {(void*)0x4000100, (void*)0x4000104, (void*)0x4000108, (void*)0x400010c};

39 static unsigned short *reg_timer_cntl[] = {(void*)0x4000102, (void*)0x4000106, (void*)0x400010a, (void*)0x400010e};

40

41 static unsigned long milli_sec;

42 static unsigned long alarm_val;

43

44 void enable_timer(int timer) {

45 *reg_timer_cntl[timer] |= TIMER_CNTL_ENABLE;

46 }

47

48 void disable_timer(int timer) {

49 *reg_timer_cntl[timer] &= ~TIMER_CNTL_ENABLE;

50 }

51

52 void reset_msec_timer(void) {

53 *reg_timer_cntl[0] &= ~TIMER_CNTL_ENABLE;

54 interrupt(INTR_TIMER0, timer_intr_handler);

55 milli_sec = 0;

56 *reg_timer[0] = USHRT_MAX - 16779;

57 *reg_timer_cntl[0] = TIMER_CNTL_INTR | TIMER_CNTL_ENABLE;

58 unmask(INTR_TIMER0);

59 }

60

61

62 unsigned long get_millisec(void) {

63 return milli_sec;

64 }

65

66 unsigned int alarm(unsigned int seconds) {

67 unsigned int prev = alarm_val;

68 alarm_val = seconds * 1000;

69 }

70

71 static void timer_intr_handler(void) {

72 milli_sec++;

73

74 if(alarm_val > 0) {

75 if(!--alarm_val) raise(SIGALRM);

76 }

77 }