hpemung/src/timers.c

#include "types.h"
#include "cpu.h"
#include "timers.h"

#define TIMER1_EXTRA 0x1
#define TIMER1_INT 0x2
#define TIMER1_WAKE 0x4
#define TIMER1_SRQ 0x8

#define TIMER_RUN 0x1
#define TIMER2_INT 0x2
#define TIMER2_WAKE 0x4
#define TIMER2_SRQ 0x8

byte timer1_control;
byte timer2_control;
byte timer1_value;
dword timer2_value;

void timer1_update( void )
{
    if ( !( timer2_control & TIMER_RUN ) )
        return;

    timer1_value--;
    timer1_value &= 0xF;

    if ( timer1_value & 0x8 ) {
        if ( timer1_control & TIMER1_WAKE ) {
            timer1_control |= TIMER1_SRQ;

            if ( cpu.shutdown ) {
                cpu.shutdown = false;
                timer1_control &= ~TIMER1_WAKE;
            }
        }
        if ( timer1_control & TIMER1_INT ) {
            timer1_control |= TIMER1_SRQ;

            if ( !cpu.shutdown )
                cpu_interrupt();
        }
    } else
        timer1_control &= ~TIMER1_SRQ;
}

void timer2_update( void )
{
    if ( !( timer2_control & TIMER_RUN ) )
        return;

    timer2_value--;
    if ( timer2_value & 0x80000000 ) {
        if ( timer2_control & TIMER2_WAKE ) {
            timer2_control |= TIMER2_SRQ;
            if ( cpu.shutdown ) {
                cpu.shutdown = 0;
                timer2_control &= ~TIMER2_WAKE;
            }
        }
        if ( timer2_control & TIMER2_INT ) {
            timer2_control |= TIMER2_SRQ;
            if ( !cpu.shutdown )
                cpu_interrupt();
        }
    } else
        timer2_control &= ~TIMER2_SRQ;
}