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// cia.c
//
// 20060803 Markku Alén
#include "cia.h"
#define TA_BIT 0
#define TA_MASK (1<<TA_BIT)
#define TB_BIT 1
#define TB_MASK (1<<TB_BIT)
#define ALRM_BIT 2
#define ALRM_MASK (1<<ALRM_BIT)
#define SP_BIT 3
#define SP_MASK (1<<SP_BIT)
#define FLAG_BIT 4
#define FLAG_MASK (1<<FLAG_BIT)
#define IR_BIT 7
#define IR_MASK (7<<IR_BIT)
#define SC_BIT 7
#define SC_MASK (7<<SC_BIT)
#define START_BIT 0
#define START_MASK (1<<START_BIT)
#define PBON_BIT 1
#define PBON_MASK (1<<PBON_BIT)
#define OUTMODE_BIT 2
#define OUTMODE_MASK (1<<OUTMODE_BIT)
#define RUNMODE_BIT 3
#define RUNMODE_MASK (1<<RUNMODE_BIT)
#define LOAD_BIT 4
#define LOAD_MASK (1<<LOAD_BIT)
#define SPMODE_BIT 6
#define SPMODE_MASK (1<<SPMODE_BIT)
#define TODIN_BIT 7
#define TODIN_MASK (1<<TODMODE_BIT)
#define INMODEA_SHIFT 5
#define INMODEA_MASK (0x1<<INMODEA_SHIFT)
#define TA_CLK (0<<INMODEA_SHIFT)
#define TA_CNT (1<<INMODEA_SHIFT)
#define INMODEB_SHIFT 5
#define INMODEB_MASK (0x3<<INMODEB_SHIFT)
#define TB_CLK (0<<INMODEB_SHIFT)
#define TB_CNT (1<<INMODEB_SHIFT)
#define TB_TMRA (2<<INMODEB_SHIFT)
#define TB_TMRA_CNT (3<<INMODEB_SHIFT)
#define ALARM_BIT 7
#define ALARM_MASK (1<<ALARM_BIT)
static unsigned char regs[16];
static void cia_interrupt_init(cia_interrupt_t *cia_interrupt)
{
cia_interrupt->mask = 0;
cia_interrupt->request = 0;
}
static void cia_interrupt_raise(cia_interrupt_t *cia_interrupt)
{
cia_interrupt->request = 1;
}
static int cia_interrupt_get_request(cia_interrupt_t *cia_interrupt)
{
int request;
request = cia_interrupt->request;
cia_interrupt->request = 0;
return request;
}
static void cia_port_init(cia_port_t *cia_port)
{
cia_port->input = 0x00;
cia_port->output = 0x00;
cia_port->direction = 0x00;
UPDATE_CIA_PORT_PINS(cia_port);
}
static void cia_port_set_data(cia_port_t *cia_port, int data)
{
cia_port->output = data;
UPDATE_CIA_PORT_PINS(cia_port);
}
static void cia_port_set_direction(cia_port_t *cia_port, int direction)
{
cia_port->direction = direction;
UPDATE_CIA_PORT_PINS(cia_port);
}
static void cia_timer_init(cia_timer_t *cia_timer)
{
cia_timer->latch = 0x0000;
cia_timer->counter = 0x0000;
cia_timer->running = 0;
cia_timer->toggle_mode = 0;
cia_timer->one_shot = 0;
cia_interrupt_init(&cia_timer->interrupt);
}
static int cia_timer_exec(cia_timer_t *cia_timer, unsigned int cycles)
{
if(!cia_timer->running)
return 0;
cia_timer->counter -= cycles;
if(cia_timer->counter >= 0)
return 0;
cia_timer->counter += cia_timer->latch;
cia_interrupt_raise(&cia_timer->interrupt);
if(cia_timer->one_shot)
cia_timer->running = 0;
return 1;
}
void cia_init(cia_t *cia)
{
cia_port_init(&cia->port_a);
cia_port_init(&cia->port_b);
cia_timer_init(&cia->timer_a);
cia_timer_init(&cia->timer_b);
cia->inmode_a = 0;
cia->inmode_b = 0;
cia->irq_pin = 0;
}
int cia_read(cia_t *cia, int address)
{
switch(address & 0x000f)
{
case 0x0000:
return cia->port_a.pins;
case 0x0001:
return cia->port_b.pins;
case 0x0002:
return cia->port_a.direction;
case 0x0003:
return cia->port_b.direction;
case 0x0004:
return cia->timer_a.counter % 256;
case 0x0005:
return cia->timer_a.counter / 256;
case 0x0006:
return cia->timer_b.counter % 256;
case 0x0007:
return cia->timer_b.counter / 256;
case 0x000d:
return 0
| (cia_interrupt_get_request(&cia->timer_a.interrupt) != 0 ? TA_MASK : 0)
| (cia_interrupt_get_request(&cia->timer_b.interrupt) != 0 ? TB_MASK : 0)
| (cia->irq_pin != 0 ? IR_MASK : 0)
;
case 0x000e:
return 0
| cia->timer_a.running
| cia->timer_a.toggle_mode
| cia->timer_a.one_shot
| cia->inmode_a
;
case 0x000f:
return 0
| cia->timer_b.running
| cia->timer_b.toggle_mode
| cia->timer_b.one_shot
| cia->inmode_b
;
default:
return regs[address % sizeof(regs)];
}
}
void cia_write(cia_t *cia, int address, int data)
{
switch(address & 0x000f)
{
case 0x0000:
cia_port_set_data(&cia->port_a, data);
break;
case 0x0001:
cia_port_set_data(&cia->port_b, data);
break;
case 0x0002:
cia_port_set_direction(&cia->port_a, data);
break;
case 0x0003:
cia_port_set_direction(&cia->port_b, data);
break;
case 0x0004:
cia->timer_a.latch = (cia->timer_a.latch & 0xff00) | (data & 0xff);
break;
case 0x0005:
cia->timer_a.latch = (cia->timer_a.latch & 0x00ff) | ((data & 0xff) << 8);
if(!cia->timer_a.running)
cia->timer_a.counter = cia->timer_a.latch;
break;
case 0x0006:
cia->timer_b.latch = (cia->timer_b.latch & 0xff00) | (data & 0xff);
break;
case 0x0007:
cia->timer_b.latch = (cia->timer_b.latch & 0x00ff) | ((data & 0xff) << 8);
if(!cia->timer_b.running)
cia->timer_b.counter = cia->timer_b.latch;
break;
case 0x000d:
if((data & TA_MASK) != 0)
cia->timer_a.interrupt.mask = data & SC_MASK;
if((data & TB_MASK) != 0)
cia->timer_b.interrupt.mask = data & SC_MASK;
break;
case 0x000e:
cia->timer_a.running = data & START_MASK;
cia->timer_a.toggle_mode = data & OUTMODE_MASK;
cia->timer_a.one_shot = data & RUNMODE_MASK;
if((data & LOAD_MASK) != 0)
cia->timer_a.counter = cia->timer_a.latch;
cia->inmode_a = data & INMODEA_MASK;
break;
case 0x000f:
cia->timer_b.running = data & START_MASK;
cia->timer_b.toggle_mode = data & OUTMODE_MASK;
cia->timer_b.one_shot = data & RUNMODE_MASK;
if((data & LOAD_MASK) != 0)
cia->timer_b.counter = cia->timer_b.latch;
cia->inmode_b = data & INMODEB_MASK;
break;
default:
regs[address % sizeof(regs)] = data;
}
}
int cia_a_port_output(cia_t *cia)
{
return cia->port_a.pins;
}
int cia_b_port_output(cia_t *cia)
{
return cia->port_b.pins;
}
void cia_port_a_input(cia_t *cia, int data)
{
cia->port_a.input = data;
UPDATE_CIA_PORT_PINS(&cia->port_a);
}
void cia_port_b_input(cia_t *cia, int data)
{
cia->port_b.input = data;
UPDATE_CIA_PORT_PINS(&cia->port_b);
}
void cia_exec(cia_t *cia, unsigned int cycles)
{
int timer_a_underflowed;
switch(cia->inmode_a)
{
case TA_CLK:
timer_a_underflowed = cia_timer_exec(&cia->timer_a, cycles);
break;
default:
timer_a_underflowed = 0;
}
switch(cia->inmode_b)
{
case TB_CLK:
cia_timer_exec(&cia->timer_b, cycles);
break;
case TB_TMRA:
if(timer_a_underflowed)
cia_timer_exec(&cia->timer_b, 1);
break;
}
cia->irq_pin = 0
| (cia->timer_a.interrupt.mask != 0 ? cia->timer_a.interrupt.request : 0)
| (cia->timer_b.interrupt.mask != 0 ? cia->timer_b.interrupt.request : 0)
;
}
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