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CookieboySweepUnit.h
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CookieboySweepUnit.h
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#ifndef COOKIEBOYSWEEPUNIT_H
#define COOKIEBOYSWEEPUNIT_H
#include "CookieboyDefs.h"
#include "CookieboyDutyUnit.h"
namespace Cookieboy
{
/*
Sweep unit increments/decrements sound unit frequency.
*/
class SweepUnit
{
public:
SweepUnit(BYTE &NRX3, BYTE &NRX4, BYTE &StatusBit, DutyUnit &dutyUnit) : NRX3(NRX3), NRX4(NRX4), StatusBit(StatusBit), Duty(dutyUnit)
{
Reset();
}
void Step(BYTE sequencerStep)
{
CurrentSequencerStep = sequencerStep;
//Sweep unit rate is 128 Hz (every 4 frame sequencer steps)
if (CurrentSequencerStep != 0 && CurrentSequencerStep != 4)
{
return;
}
//Sweep time is positive
if (NRX0SweepPeriod)//Sweep function
{
ClockCounter--;
if (ClockCounter <= 0)
{
ClockCounter += NRX0SweepPeriod;
if (SweepEnabled)
{
SweepStep();
}
}
}
//If sweep time is zero timer treats it as 8
else
{
ClockCounter--;
if (ClockCounter <= 0)
{
ClockCounter += 8;
}
}
}
void Reset()
{
NRX0 = 0;
oldNRX4 = 0;
ClockCounter = 0;
ShadowReg = ((NRX4 & 0x7) << 8) | NRX3;
SweepEnabled = false;
}
void NRX0Changed(BYTE value)
{
NRX0 = value;
NRX0SweepPeriod = (NRX0 >> 4) & 0x7;
NRX0SweepDirection = (NRX0 >> 3) & 0x1;
NRX0SweepShiftLength = NRX0 & 0x7;
//Clearing negate mode after at least one calculation was made in negate mode disables channel
if (!NRX0SweepDirection && NegateMode)
{
StatusBit = 0;
}
}
BYTE GetNRX0() { return NRX0 | 0x80; }
void NRX4Changed(BYTE value)
{
oldNRX4 = value;
if (value >> 7)
{
ShadowReg = ((NRX4 & 0x7) << 8) | NRX3;
ClockCounter = NRX0SweepPeriod;
NegateMode = false;
//If sweep time is zero timer treats it as 8
if (!NRX0SweepPeriod)
{
ClockCounter = 8;
}
SweepEnabled = NRX0SweepShiftLength || NRX0SweepPeriod;
if (NRX0SweepShiftLength)
{
CalculateFrequency();
}
}
}
private:
void SweepStep()
{
int newFreq = CalculateFrequency();
if ((newFreq <= 2047.0) && NRX0SweepShiftLength)
{
NRX3 = newFreq & 0xFF;
NRX4 = (NRX4 & 0xF8) | ((newFreq >> 8) & 0x7);
Duty.NRX3Changed(NRX3);
Duty.NRX4Changed(NRX4);
ShadowReg = newFreq;
//Frequency calculation and overflow check AGAIN but not saving new frequency
CalculateFrequency();
}
}
int CalculateFrequency()
{
int newFreq = ShadowReg;
int shadowRegShift = ShadowReg >> NRX0SweepShiftLength;
if (NRX0SweepDirection)//Decrease mode
{
//If next frequency is negative then using current frequency
if (ShadowReg >= shadowRegShift)
{
newFreq = ShadowReg - shadowRegShift;
}
NegateMode = true;
}
else//Increase mode
{
newFreq = ShadowReg + shadowRegShift;
NegateMode = false;
}
//If frequency exeeds maximum sound disabled
if (newFreq > 2047.0)
{
StatusBit = 0;
}
return newFreq;
}
BYTE NRX0; //Sweep register (R/W)
//Bit 6-4 - Sweep Time
//Bit 3 - Sweep Increase/Decrease
// 0: Addition (frequency increases)
// 1: Subtraction (frequency decreases)
//Bit 2-0 - Number of sweep shift (n: 0-7)
BYTE &NRX3;
BYTE oldNRX4;
BYTE &NRX4;
BYTE NRX0SweepPeriod;
BYTE NRX0SweepDirection;
BYTE NRX0SweepShiftLength;
DutyUnit &Duty;
int ShadowReg;
int ClockCounter;
bool SweepEnabled;
bool NegateMode;//Indicates that at least one calculation was made in negate mode
BYTE &StatusBit;
BYTE CurrentSequencerStep;
};
}
#endif