80 lines
1.9 KiB
C
80 lines
1.9 KiB
C
/*
|
|
|
|
This file is part of Emu-Pizza
|
|
|
|
Emu-Pizza is free software: you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation, either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
Emu-Pizza is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with Emu-Pizza. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
*/
|
|
|
|
#include "cycles.h"
|
|
#include "interrupt.h"
|
|
#include "mmu.h"
|
|
#include "timer.h"
|
|
|
|
/* pointer to interrupt flags (handy) */
|
|
interrupts_flags_t *timer_if;
|
|
|
|
|
|
void timer_init()
|
|
{
|
|
/* reset values */
|
|
timer.next = 256;
|
|
timer.sub = 0;
|
|
|
|
/* pointer to interrupt flags */
|
|
timer_if = mmu_addr(0xFF0F);
|
|
}
|
|
|
|
void timer_write_reg(uint16_t a, uint8_t v)
|
|
{
|
|
switch (a)
|
|
{
|
|
case 0xFF04: timer.div = 0; return;
|
|
case 0xFF05: timer.cnt = v; return;
|
|
case 0xFF06: timer.mod = v; return;
|
|
case 0xFF07: timer.ctrl = v;
|
|
}
|
|
|
|
if (timer.ctrl & 0x04)
|
|
timer.active = 1;
|
|
else
|
|
timer.active = 0;
|
|
|
|
switch (timer.ctrl & 0x03)
|
|
{
|
|
case 0x00: timer.threshold = 1024; break;
|
|
case 0x01: timer.threshold = 16; break;
|
|
case 0x02: timer.threshold = 64; break;
|
|
case 0x03: timer.threshold = 256; break;
|
|
}
|
|
|
|
if (timer.active)
|
|
timer.sub_next = cycles.cnt + timer.threshold;
|
|
}
|
|
|
|
uint8_t timer_read_reg(uint16_t a)
|
|
{
|
|
switch (a)
|
|
{
|
|
case 0xFF04: return timer.div;
|
|
case 0xFF05: return timer.cnt;
|
|
case 0xFF06: return timer.mod;
|
|
case 0xFF07: return timer.ctrl;
|
|
}
|
|
|
|
return 0xFF;
|
|
}
|
|
|
|
|