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CIA.cpp
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CIA.cpp
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/*
Frodo, Commodore 64 emulator for the iPhone
Copyright (C) 1994-1997,2002 Christian Bauer
See gpl.txt for license information.
This program 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.
This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* CIA.cpp - 6526 emulation
*
* Frodo (C) 1994-1997,2002 Christian Bauer
*
*
* Notes:
* ------
*
* - The EmulateLine() function is called for every emulated raster
* line. It counts down the timers and triggers interrupts if
* necessary.
* - The TOD clocks are counted by CountTOD() during the VBlank, so
* the input frequency is 50Hz
* - The fields KeyMatrix and RevMatrix contain one bit for each
* key on the C64 keyboard (0: key pressed, 1: key released).
* KeyMatrix is used for normal keyboard polling (PRA->PRB),
* RevMatrix for reversed polling (PRB->PRA).
*
* Incompatibilities:
* ------------------
*
* - The TOD clock should not be stopped on a read access, but
* latched
* - The SDR interrupt is faked
*/
#include "sysdeps.h"
#include "CIA.h"
#include "CPUC64.h"
#include "CPU1541.h"
#include "VIC.h"
#include "Prefs.h"
/*
* Constructors
*/
MOS6526::MOS6526(MOS6510 *CPU) : the_cpu(CPU) {}
MOS6526_1::MOS6526_1(MOS6510 *CPU, MOS6569 *VIC) : MOS6526(CPU), the_vic(VIC) { type=1; }
MOS6526_2::MOS6526_2(MOS6510 *CPU, MOS6569 *VIC, MOS6502_1541 *CPU1541) :
MOS6526(CPU), the_vic(VIC), the_cpu_1541(CPU1541) { type=2; }
/*
* Switch from standard emulation to single cycle emulation
*/
void MOS6526::SwitchToSC(void)
{
ta_irq_next_cycle = false;
tb_irq_next_cycle = false;
has_new_cra = false;
has_new_crb = false;
ta_state = ta_cnt_phi2 ? T_COUNT : T_STOP;
tb_state = (tb_cnt_phi2 || tb_cnt_ta) ? T_COUNT : T_STOP;
CyclesTillAction = 1;
CyclesTillActionCnt = 1;
}
/*
* Switch from single cycle emulation to standard emulation
*/
void MOS6526::SwitchToStandard(void)
{
UpdateTATB(false);
if(has_new_cra)
{
cra = new_cra & 0xef;
if (new_cra & 0x10) // Force load
ta = latcha;
}
if(has_new_crb)
{
crb = new_crb & 0xef;
if (new_crb & 0x10) // Force load
tb = latchb;
}
if(ta_irq_next_cycle)
TriggerInterrupt(1);
if(tb_irq_next_cycle)
TriggerInterrupt(2);
}
/*
* Reset the CIA
*/
void MOS6526::Reset(void)
{
pra = prb = ddra = ddrb = 0;
ta = tb = 0xffff;
latcha = latchb = 1;
tod_10ths = tod_sec = tod_min = tod_hr = 0;
alm_10ths = alm_sec = alm_min = alm_hr = 0;
sdr = icr = cra = crb = int_mask = 0;
tod_halt = ta_cnt_phi2 = tb_cnt_phi2 = tb_cnt_ta = false;
tod_divider = 0;
ta_irq_next_cycle = tb_irq_next_cycle = false;
ta_state = tb_state = T_STOP;
CyclesTillAction = 1;
CyclesTillAction = 1;
}
void MOS6526_1::Reset(void)
{
MOS6526::Reset();
// Clear keyboard matrix and joystick states
for (int i=0; i<8; i++)
KeyMatrix[i] = RevMatrix[i] = 0xff;
Joystick1 = Joystick2 = 0xff;
prev_lp = 0x10;
}
void MOS6526_2::Reset(void)
{
MOS6526::Reset();
// VA14/15 = 0
the_vic->ChangedVA(0);
// IEC
IECLines = 0xd0;
}
/*
* Get CIA state
*/
void MOS6526::GetState(MOS6526State *cs)
{
cs->pra = pra;
cs->prb = prb;
cs->ddra = ddra;
cs->ddrb = ddrb;
cs->ta_lo = ta & 0xff;
cs->ta_hi = ta >> 8;
cs->tb_lo = tb & 0xff;
cs->tb_hi = tb >> 8;
cs->latcha = latcha;
cs->latchb = latchb;
cs->cra = cra;
cs->crb = crb;
cs->tod_10ths = tod_10ths;
cs->tod_sec = tod_sec;
cs->tod_min = tod_min;
cs->tod_hr = tod_hr;
cs->alm_10ths = alm_10ths;
cs->alm_sec = alm_sec;
cs->alm_min = alm_min;
cs->alm_hr = alm_hr;
cs->sdr = sdr;
cs->int_data = icr;
cs->int_mask = int_mask;
cs->CyclesTillAction = CyclesTillAction;
cs->CyclesTillActionCnt = CyclesTillActionCnt;
cs->has_new_cra = has_new_cra;
cs->has_new_crb = has_new_crb;
cs->new_cra = new_cra;
cs->new_crb = new_crb;
cs->ta_irq_next_cycle = ta_irq_next_cycle;
cs->tb_irq_next_cycle = tb_irq_next_cycle;
cs->ta_state = ta_state;
cs->tb_state = tb_state;
cs->ta_cnt_phi2 = ta_cnt_phi2;
cs->tb_cnt_phi2 = tb_cnt_phi2;
cs->tb_cnt_ta = tb_cnt_ta;
cs->more_info = GetMoreInfo();
}
/*
* Restore CIA state
*/
void MOS6526::SetState(MOS6526State *cs)
{
pra = cs->pra;
prb = cs->prb;
ddra = cs->ddra;
ddrb = cs->ddrb;
ta = (cs->ta_hi << 8) | cs->ta_lo;
tb = (cs->tb_hi << 8) | cs->tb_lo;
latcha = cs->latcha;
latchb = cs->latchb;
cra = cs->cra;
crb = cs->crb;
tod_10ths = cs->tod_10ths;
tod_sec = cs->tod_sec;
tod_min = cs->tod_min;
tod_hr = cs->tod_hr;
alm_10ths = cs->alm_10ths;
alm_sec = cs->alm_sec;
alm_min = cs->alm_min;
alm_hr = cs->alm_hr;
sdr = cs->sdr;
icr = cs->int_data;
int_mask = cs->int_mask;
tod_halt = false;
CyclesTillAction = cs->CyclesTillAction;
CyclesTillActionCnt = cs->CyclesTillActionCnt;
has_new_cra = cs->has_new_cra;
has_new_crb = cs->has_new_crb;
new_cra = cs->new_cra;
new_crb = cs->new_crb;
ta_irq_next_cycle = cs->ta_irq_next_cycle;
tb_irq_next_cycle = cs->tb_irq_next_cycle;
ta_state = cs->ta_state;
tb_state = cs->tb_state;
ta_cnt_phi2 = cs->ta_cnt_phi2;
tb_cnt_phi2 = cs->tb_cnt_phi2;
tb_cnt_ta = cs->tb_cnt_ta;
SetMoreInfo(cs->more_info);
}
/*
* Read from register (CIA 1)
*/
void MOS6526_1::UpdateDataPorts(void)
{
uint8 ret = pra | ~ddra;
uint8 tst = (prb | ~ddrb) & Joystick1;
if (!(tst & 0x01)) ret &= RevMatrix[0]; // AND all active columns
if (!(tst & 0x02)) ret &= RevMatrix[1];
if (!(tst & 0x04)) ret &= RevMatrix[2];
if (!(tst & 0x08)) ret &= RevMatrix[3];
if (!(tst & 0x10)) ret &= RevMatrix[4];
if (!(tst & 0x20)) ret &= RevMatrix[5];
if (!(tst & 0x40)) ret &= RevMatrix[6];
if (!(tst & 0x80)) ret &= RevMatrix[7];
dataport1 = ret & Joystick2;
ret = ~ddrb;
tst = (pra | ~ddra) & Joystick2;
if (!(tst & 0x01)) ret &= KeyMatrix[0]; // AND all active rows
if (!(tst & 0x02)) ret &= KeyMatrix[1];
if (!(tst & 0x04)) ret &= KeyMatrix[2];
if (!(tst & 0x08)) ret &= KeyMatrix[3];
if (!(tst & 0x10)) ret &= KeyMatrix[4];
if (!(tst & 0x20)) ret &= KeyMatrix[5];
if (!(tst & 0x40)) ret &= KeyMatrix[6];
if (!(tst & 0x80)) ret &= KeyMatrix[7];
dataport2 = (ret | (prb & ddrb)) & Joystick1;
}
uint8 MOS6526_1::ReadRegister(uint16 adr)
{
switch (adr) {
case 0x00: return dataport1;
case 0x01: return dataport2;
case 0x02: return ddra;
case 0x03: return ddrb;
case 0x04:
if(ThePrefs.SingleCycleEmulation)
UpdateTATB(false);
return ta;
case 0x05:
if(ThePrefs.SingleCycleEmulation)
UpdateTATB(false);
return ta >> 8;
case 0x06:
if(ThePrefs.SingleCycleEmulation)
UpdateTATB(false);
return tb;
case 0x07:
if(ThePrefs.SingleCycleEmulation)
UpdateTATB(false);
return tb >> 8;
case 0x08: tod_halt = false; return tod_10ths;
case 0x09: return tod_sec;
case 0x0a: return tod_min;
case 0x0b: tod_halt = true; return tod_hr;
case 0x0c: return sdr;
case 0x0d: {
uint8 ret = icr; // Read and clear ICR
icr = 0;
the_cpu->ClearCIAIRQ(); // Clear IRQ
return ret;
}
case 0x0e: return cra;
case 0x0f: return crb;
}
return 0; // Can't happen
}
/*
* Read from register (CIA 2)
*/
uint8 MOS6526_2::ReadRegister(uint16 adr)
{
switch (adr) {
case 0x00:
return (pra | ~ddra) & 0x3f
| IECLines & the_cpu_1541->IECLines;
case 0x01: return prb | ~ddrb;
case 0x02: return ddra;
case 0x03: return ddrb;
case 0x04:
if(ThePrefs.SingleCycleEmulation)
UpdateTATB(false);
return ta;
case 0x05:
if(ThePrefs.SingleCycleEmulation)
UpdateTATB(false);
return ta >> 8;
case 0x06:
if(ThePrefs.SingleCycleEmulation)
UpdateTATB(false);
return tb;
case 0x07:
if(ThePrefs.SingleCycleEmulation)
UpdateTATB(false);
return tb >> 8;
case 0x08: tod_halt = false; return tod_10ths;
case 0x09: return tod_sec;
case 0x0a: return tod_min;
case 0x0b: tod_halt = true; return tod_hr;
case 0x0c: return sdr;
case 0x0d: {
uint8 ret = icr; // Read and clear ICR
icr = 0;
the_cpu->ClearNMI(); // Clear NMI
return ret;
}
case 0x0e: return cra;
case 0x0f: return crb;
}
return 0; // Can't happen
}
/*
* Write to register (CIA 1)
*/
// Write to port B, check for lightpen interrupt
inline void MOS6526_1::check_lp(void)
{
if ((prb | ~ddrb) & 0x10 != prev_lp)
the_vic->TriggerLightpen();
prev_lp = (prb | ~ddrb) & 0x10;
}
void MOS6526_1::WriteRegister(uint16 adr, uint8 byte)
{
switch (adr) {
case 0x0:
pra = byte;
UpdateDataPorts();
break;
case 0x1:
prb = byte;
UpdateDataPorts();
check_lp();
break;
case 0x2:
ddra = byte;
UpdateDataPorts();
break;
case 0x3:
ddrb = byte;
UpdateDataPorts();
check_lp();
break;
case 0x4: latcha = (latcha & 0xff00) | byte; break;
case 0x5:
latcha = (latcha & 0xff) | (byte << 8);
if (!(cra & 1)) // Reload timer if stopped
ta = latcha;
break;
case 0x6: latchb = (latchb & 0xff00) | byte; break;
case 0x7:
latchb = (latchb & 0xff) | (byte << 8);
if (!(crb & 1)) // Reload timer if stopped
tb = latchb;
break;
case 0x8:
if (crb & 0x80)
alm_10ths = byte & 0x0f;
else
tod_10ths = byte & 0x0f;
break;
case 0x9:
if (crb & 0x80)
alm_sec = byte & 0x7f;
else
tod_sec = byte & 0x7f;
break;
case 0xa:
if (crb & 0x80)
alm_min = byte & 0x7f;
else
tod_min = byte & 0x7f;
break;
case 0xb:
if (crb & 0x80)
alm_hr = byte & 0x9f;
else
tod_hr = byte & 0x9f;
break;
case 0xc:
sdr = byte;
TriggerInterrupt(8); // Fake SDR interrupt for programs that need it
break;
case 0xd:
if(ThePrefs.SingleCycleEmulation)
{
if (byte & 0x80)
int_mask |= byte & 0x7f;
else
int_mask &= ~byte;
if (icr & int_mask & 0x1f) { // Trigger IRQ if pending
icr |= 0x80;
the_cpu->TriggerCIAIRQ();
}
}
else
{
if (ThePrefs.CIAIRQHack) // Hack for addressing modes that read from the address
icr = 0;
if (byte & 0x80) {
int_mask |= byte & 0x7f;
if (icr & int_mask & 0x1f) { // Trigger IRQ if pending
icr |= 0x80;
the_cpu->TriggerCIAIRQ();
}
} else
int_mask &= ~byte;
}
break;
case 0xe:
if(ThePrefs.SingleCycleEmulation)
{
UpdateTATB(true);
has_new_cra = true; // Delay write by 1 cycle
new_cra = byte;
ta_cnt_phi2 = ((byte & 0x20) == 0x00);
}
else
{
cra = byte & 0xef;
if (byte & 0x10) // Force load
ta = latcha;
ta_cnt_phi2 = ((byte & 0x21) == 0x01);
}
break;
case 0xf:
if(ThePrefs.SingleCycleEmulation)
{
UpdateTATB(true);
has_new_crb = true; // Delay write by 1 cycle
new_crb = byte;
tb_cnt_phi2 = ((byte & 0x60) == 0x00);
tb_cnt_ta = ((byte & 0x60) == 0x40);
}
else
{
crb = byte & 0xef;
if (byte & 0x10) // Force load
tb = latchb;
tb_cnt_phi2 = ((byte & 0x61) == 0x01);
tb_cnt_ta = ((byte & 0x61) == 0x41);
}
break;
}
}
/*
* Write to register (CIA 2)
*/
void MOS6526_2::WriteRegister(uint16 adr, uint8 byte)
{
uint8 old_lines;
switch (adr) {
case 0x0:{
pra = byte;
if(ThePrefs.SingleCycleEmulation)
{
the_vic->ChangedVA(~(pra | ~ddra) & 3);
old_lines = IECLines;
IECLines = (~byte << 2) & 0x80 // DATA
| (~byte << 2) & 0x40 // CLK
| (~byte << 1) & 0x10; // ATN
}
else
{
byte = ~pra & ddra;
the_vic->ChangedVA(byte & 3);
old_lines = IECLines;
IECLines = (byte << 2) & 0x80 // DATA
| (byte << 2) & 0x40 // CLK
| (byte << 1) & 0x10; // ATN
}
if ((IECLines ^ old_lines) & 0x10) { // ATN changed
the_cpu_1541->NewATNState();
if (old_lines & 0x10) // ATN 1->0
the_cpu_1541->IECInterrupt();
}
break;
}
case 0x1: prb = byte; break;
case 0x2:
ddra = byte;
the_vic->ChangedVA(~(pra | ~ddra) & 3);
break;
case 0x3: ddrb = byte; break;
case 0x4: latcha = (latcha & 0xff00) | byte; break;
case 0x5:
latcha = (latcha & 0xff) | (byte << 8);
if (!(cra & 1)) // Reload timer if stopped
ta = latcha;
break;
case 0x6: latchb = (latchb & 0xff00) | byte; break;
case 0x7:
latchb = (latchb & 0xff) | (byte << 8);
if (!(crb & 1)) // Reload timer if stopped
tb = latchb;
break;
case 0x8:
if (crb & 0x80)
alm_10ths = byte & 0x0f;
else
tod_10ths = byte & 0x0f;
break;
case 0x9:
if (crb & 0x80)
alm_sec = byte & 0x7f;
else
tod_sec = byte & 0x7f;
break;
case 0xa:
if (crb & 0x80)
alm_min = byte & 0x7f;
else
tod_min = byte & 0x7f;
break;
case 0xb:
if (crb & 0x80)
alm_hr = byte & 0x9f;
else
tod_hr = byte & 0x9f;
break;
case 0xc:
sdr = byte;
TriggerInterrupt(8); // Fake SDR interrupt for programs that need it
break;
case 0xd:
if(ThePrefs.SingleCycleEmulation)
{
if (byte & 0x80)
int_mask |= byte & 0x7f;
else
int_mask &= ~byte;
if (icr & int_mask & 0x1f) { // Trigger NMI if pending
icr |= 0x80;
the_cpu->TriggerNMI();
}
}
else
{
if (ThePrefs.CIAIRQHack)
icr = 0;
if (byte & 0x80) {
int_mask |= byte & 0x7f;
if (icr & int_mask & 0x1f) { // Trigger NMI if pending
icr |= 0x80;
the_cpu->TriggerNMI();
}
} else
int_mask &= ~byte;
}
break;
case 0xe:
if(ThePrefs.SingleCycleEmulation)
{
UpdateTATB(true);
has_new_cra = true; // Delay write by 1 cycle
new_cra = byte;
ta_cnt_phi2 = ((byte & 0x20) == 0x00);
}
else
{
cra = byte & 0xef;
if (byte & 0x10) // Force load
ta = latcha;
ta_cnt_phi2 = ((byte & 0x21) == 0x01);
}
break;
case 0xf:
if(ThePrefs.SingleCycleEmulation)
{
UpdateTATB(true);
has_new_crb = true; // Delay write by 1 cycle
new_crb = byte;
tb_cnt_phi2 = ((byte & 0x60) == 0x00);
tb_cnt_ta = ((byte & 0x60) == 0x40);
}
else
{
crb = byte & 0xef;
if (byte & 0x10) // Force load
tb = latchb;
tb_cnt_phi2 = ((byte & 0x61) == 0x01);
tb_cnt_ta = ((byte & 0x61) == 0x41);
}
break;
}
}
inline void MOS6526::UpdateTATB(bool ResetCyclesTillAction)
{
uint16 ElapsedCycles = CyclesTillAction - CyclesTillActionCnt;
if(ElapsedCycles > 0)
{
// Check, if we have to update ta
if(ta_cnt_phi2 && ta_state == T_COUNT && ta > 0)
ta = ta - ElapsedCycles;
// Check, if we have to update tb
if(tb_cnt_phi2 && tb_state == T_COUNT && tb > 0)
tb = tb - ElapsedCycles;
}
if(ResetCyclesTillAction)
{
// Called from WriteRegister -> next action after one cycle
CyclesTillAction = 1;
CyclesTillActionCnt = 1;
}
else
CyclesTillAction = CyclesTillActionCnt;
}
void MOS6526::EmulateCycles(void)
{
bool ta_underflow = false;
// Trigger pending interrupts
if (ta_irq_next_cycle)
{
ta_irq_next_cycle = false;
TriggerInterrupt(1);
}
if (tb_irq_next_cycle)
{
tb_irq_next_cycle = false;
TriggerInterrupt(2);
}
// Timer A state machine
switch (ta_state)
{
case T_WAIT_THEN_COUNT:
ta_state = T_COUNT; // fall through
case T_STOP:
goto ta_idle;
case T_LOAD_THEN_STOP:
ta_state = T_STOP;
ta = latcha; // Reload timer
goto ta_idle;
case T_LOAD_THEN_COUNT:
ta_state = T_COUNT;
ta = latcha; // Reload timer
goto ta_idle;
case T_LOAD_THEN_WAIT_THEN_COUNT:
ta_state = T_WAIT_THEN_COUNT;
if (ta == 1)
goto ta_interrupt; // Interrupt if timer == 1
else
{
ta = latcha; // Reload timer
goto ta_idle;
}
case T_COUNT:
goto ta_count;
case T_COUNT_THEN_STOP:
ta_state = T_STOP;
goto ta_count;
}
// Count timer A
ta_count:
if (ta_cnt_phi2)
{
if(ta > 0)
ta = ta - (CyclesTillAction - CyclesTillActionCnt);
if (!ta)
{ // underflow?
if (ta_state != T_STOP)
{
ta_interrupt:
ta = latcha; // Reload timer
ta_irq_next_cycle = true; // Trigger interrupt in next cycle
icr |= 1; // But set ICR bit now
if (cra & 8) { // One-shot?
cra &= 0xfe; // Yes, stop timer
new_cra &= 0xfe;
ta_state = T_LOAD_THEN_STOP; // Reload in next cycle
} else
ta_state = T_LOAD_THEN_COUNT; // No, delay one cycle (and reload)
}
ta_underflow = true;
}
}
// Delayed write to CRA?
ta_idle:
if (has_new_cra)
{
switch (ta_state)
{
case T_STOP:
case T_LOAD_THEN_STOP:
if (new_cra & 1) { // Timer started, wasn't running
if (new_cra & 0x10) // Force load
ta_state = T_LOAD_THEN_WAIT_THEN_COUNT;
else // No force load
ta_state = T_WAIT_THEN_COUNT;
} else { // Timer stopped, was already stopped
if (new_cra & 0x10) // Force load
ta_state = T_LOAD_THEN_STOP;
}
break;
case T_COUNT:
if (new_cra & 1) { // Timer started, was already running
if (new_cra & 0x10) // Force load
ta_state = T_LOAD_THEN_WAIT_THEN_COUNT;
} else { // Timer stopped, was running
if (new_cra & 0x10) // Force load
ta_state = T_LOAD_THEN_STOP;
else // No force load
ta_state = T_COUNT_THEN_STOP;
}
break;
case T_LOAD_THEN_COUNT:
case T_WAIT_THEN_COUNT:
if (new_cra & 1) {
if (new_cra & 8) { // One-shot?
new_cra &= 0xfe; // Yes, stop timer
ta_state = T_STOP;
} else if (new_cra & 0x10) // Force load
ta_state = T_LOAD_THEN_WAIT_THEN_COUNT;
} else {
ta_state = T_STOP;
}
break;
}
cra = new_cra & 0xef;
has_new_cra = false;
}
// Timer B state machine
switch (tb_state)
{
case T_WAIT_THEN_COUNT:
tb_state = T_COUNT; // fall through
case T_STOP:
goto tb_idle;
case T_LOAD_THEN_STOP:
tb_state = T_STOP;
tb = latchb; // Reload timer
goto tb_idle;
case T_LOAD_THEN_COUNT:
tb_state = T_COUNT;
tb = latchb; // Reload timer
goto tb_idle;
case T_LOAD_THEN_WAIT_THEN_COUNT:
tb_state = T_WAIT_THEN_COUNT;
if (tb == 1)
goto tb_interrupt; // Interrupt if timer == 1
else {
tb = latchb; // Reload timer
goto tb_idle;
}
case T_COUNT:
goto tb_count;
case T_COUNT_THEN_STOP:
tb_state = T_STOP;
goto tb_count;
}
// Count timer B
tb_count:
if (tb_cnt_phi2 || (tb_cnt_ta && ta_underflow))
{
if(tb > 0)
{
if(tb_cnt_phi2)
tb = tb - (CyclesTillAction - CyclesTillActionCnt);
else
--tb;
}
if (!tb)
{ // underflow?
if (tb_state != T_STOP)
{
tb_interrupt:
tb = latchb; // Reload timer
tb_irq_next_cycle = true; // Trigger interrupt in next cycle
icr |= 2; // But set ICR bit now
if (crb & 8) { // One-shot?
crb &= 0xfe; // Yes, stop timer
new_crb &= 0xfe;
tb_state = T_LOAD_THEN_STOP; // Reload in next cycle
} else
tb_state = T_LOAD_THEN_COUNT; // No, delay one cycle (and reload)
}
}
}
// Delayed write to CRB?
tb_idle:
if (has_new_crb)
{
switch (tb_state)
{
case T_STOP:
case T_LOAD_THEN_STOP:
if (new_crb & 1) { // Timer started, wasn't running
if (new_crb & 0x10) // Force load
tb_state = T_LOAD_THEN_WAIT_THEN_COUNT;
else // No force load
tb_state = T_WAIT_THEN_COUNT;
} else { // Timer stopped, was already stopped
if (new_crb & 0x10) // Force load
tb_state = T_LOAD_THEN_STOP;
}
break;
case T_COUNT:
if (new_crb & 1) { // Timer started, was already running
if (new_crb & 0x10) // Force load
tb_state = T_LOAD_THEN_WAIT_THEN_COUNT;
} else { // Timer stopped, was running
if (new_crb & 0x10) // Force load
tb_state = T_LOAD_THEN_STOP;
else // No force load
tb_state = T_COUNT_THEN_STOP;
}
break;
case T_LOAD_THEN_COUNT:
case T_WAIT_THEN_COUNT:
if (new_crb & 1) {
if (new_crb & 8) { // One-shot?
new_crb &= 0xfe; // Yes, stop timer
tb_state = T_STOP;
} else if (new_crb & 0x10) // Force load
tb_state = T_LOAD_THEN_WAIT_THEN_COUNT;
} else {
tb_state = T_STOP;
}
break;
}
crb = new_crb & 0xef;
has_new_crb = false;
}
// Calculate cycles till next action
CyclesTillAction = 65535;
if(ta_state == T_COUNT)
{
if(ta_cnt_phi2 && ta > 0)
CyclesTillAction = ta;
else
CyclesTillAction = 1;
}
if((ta_state != T_COUNT && ta_state != T_STOP)
|| (tb_state != T_COUNT && tb_state != T_STOP)
|| ta_irq_next_cycle || tb_irq_next_cycle)
CyclesTillAction = 1;
if(tb_state == T_COUNT)
{
if(tb_cnt_phi2 && tb > 0)
{
if(tb < CyclesTillAction)
CyclesTillAction = tb;
}
else
CyclesTillAction = 1;
}
//CyclesTillAction = 1;
CyclesTillActionCnt = CyclesTillAction;
}
/*
* Count CIA TOD clock (called during VBlank)
*/
void MOS6526::CountTOD(void)
{
uint8 lo, hi;
// Decrement frequency divider
if (tod_divider)
tod_divider--;
else {
// Reload divider according to 50/60 Hz flag
if (cra & 0x80)
tod_divider = 4;
else
tod_divider = 5;
// 1/10 seconds
tod_10ths++;
if (tod_10ths > 9) {
tod_10ths = 0;
// Seconds
lo = (tod_sec & 0x0f) + 1;
hi = tod_sec >> 4;
if (lo > 9) {
lo = 0;
hi++;