1 /*

2 gbasys - a gameboy advance hardware abstraction library

3 Copyright (C) 2004-2014 John Tsiombikas <nuclear@member.fsf.org>

4

5 This program is free software: you can redistribute it and/or modify

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

7 the Free Software Foundation, either version 3 of the License, or

8 (at your option) any later version.

9

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

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

12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

13 GNU General Public License for more details.

14

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

16 along with this program. If not, see <http://www.gnu.org/licenses/>.

17 */

18 #include <limits.h>

19 #include "intr.h"

20 #include "signal.h"

21

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

23 #define TIMER_CNTL_CLK 0

24 #define TIMER_CNTL_CLK64 1

25 #define TIMER_CNTL_CLK256 2

26 #define TIMER_CNTL_CLK1024 3

27

28 /* control bits */

29 #define TIMER_CNTL_COUNTUP 4

30 #define TIMER_CNTL_INTR 0x40

31 #define TIMER_CNTL_ENABLE 0x80

32

33 static void timer_intr_handler(void);

34

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

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

37

38 static unsigned long milli_sec;

39 static unsigned long alarm_val;

40

41 void enable_timer(int timer) {

42 *reg_timer_cntl[timer] |= TIMER_CNTL_ENABLE;

43 }

44

45 void disable_timer(int timer) {

46 *reg_timer_cntl[timer] &= ~TIMER_CNTL_ENABLE;

47 }

48

49 void reset_msec_timer(void) {

50 *reg_timer_cntl[0] &= ~TIMER_CNTL_ENABLE;

51 interrupt(INTR_TIMER0, timer_intr_handler);

52 milli_sec = 0;

53 *reg_timer[0] = USHRT_MAX - 16779;

54 *reg_timer_cntl[0] = TIMER_CNTL_INTR | TIMER_CNTL_ENABLE;

55 unmask(INTR_TIMER0);

56 }

57

58

59 unsigned long get_millisec(void) {

60 return milli_sec;

61 }

62

63 unsigned int alarm(unsigned int seconds) {

64 unsigned int prev = alarm_val;

65 alarm_val = seconds * 1000;

66 }

67

68 static void timer_intr_handler(void) {

69 milli_sec++;

70

71 if(alarm_val > 0) {

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

73 }

74 }