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Made an attempt at NMI usurption of IRQ/BRK.

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This commit is contained in:
Thomas Harte 2016-06-29 20:59:45 -04:00
parent c02226bc41
commit 41809d4597
1 changed files with 26 additions and 15 deletions
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41
Processors/6502/CPU6502.hpp
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@ -92,7 +92,11 @@ template <class T> class Processor {
enum MicroOp {
CycleFetchOperation, CycleFetchOperand, OperationDecodeOperation, CycleIncPCPushPCH,
CyclePushPCH, CyclePushPCL, CyclePushA, CyclePushOperand,
CycleSetIReadBRKLow, CycleReadBRKHigh,
OperationSetI,
OperationBRKPickVector, OperationNMIPickVector, OperationRSTPickVector,
CycleReadVectorLow, CycleReadVectorHigh,
CycleReadFromS, CycleReadFromPC,
CyclePullOperand, CyclePullPCL, CyclePullPCH, CyclePullA,
CycleNoWritePush,
@ -122,7 +126,6 @@ template <class T> class Processor {
OperationLAS, CycleAddSignedOperandToPC, OperationSetFlagsFromOperand, OperationSetOperandFromFlagsWithBRKSet,
OperationSetOperandFromFlags,
OperationSetFlagsFromA,
CycleReadRSTLow, CycleReadRSTHigh, CycleReadNMILow, CycleReadNMIHigh,
CycleScheduleJam
};
@ -272,7 +275,7 @@ template <class T> class Processor {
static const MicroOp operations[256][10] = {
/* 0x00 BRK */ Program(CycleIncPCPushPCH, CyclePushPCL, OperationSetOperandFromFlagsWithBRKSet, CyclePushOperand, CycleSetIReadBRKLow, CycleReadBRKHigh),
/* 0x00 BRK */ Program(CycleIncPCPushPCH, CyclePushPCL, OperationBRKPickVector, OperationSetOperandFromFlagsWithBRKSet, CyclePushOperand, OperationSetI, CycleReadVectorLow, CycleReadVectorHigh),
/* 0x01 ORA x, ind */ IndexedIndirectRead(OperationORA),
/* 0x02 JAM */ JAM, /* 0x03 ASO x, ind */ IndexedIndirectReadModifyWrite(OperationASO),
/* 0x04 NOP zpg */ ZeroNop(), /* 0x05 ORA zpg */ ZeroRead(OperationORA),
@ -481,9 +484,10 @@ template <class T> class Processor {
CycleFetchOperand,
CycleNoWritePush,
CycleNoWritePush,
OperationRSTPickVector,
CycleNoWritePush,
CycleReadRSTLow,
CycleReadRSTHigh,
CycleReadVectorLow,
CycleReadVectorHigh,
OperationMoveToNextProgram
};
return reset;
@ -500,10 +504,12 @@ template <class T> class Processor {
CycleFetchOperand,
CyclePushPCH,
CyclePushPCL,
OperationBRKPickVector,
OperationSetOperandFromFlags,
CyclePushOperand,
CycleSetIReadBRKLow,
CycleReadBRKHigh,
OperationSetI,
CycleReadVectorLow,
CycleReadVectorHigh,
OperationMoveToNextProgram
};
return reset;
@ -520,10 +526,11 @@ template <class T> class Processor {
CycleFetchOperand,
CyclePushPCH,
CyclePushPCL,
OperationNMIPickVector,
OperationSetOperandFromFlags,
CyclePushOperand,
CycleReadNMILow,
CycleReadNMIHigh,
CycleReadVectorLow,
CycleReadVectorHigh,
OperationMoveToNextProgram
};
return reset;
@ -693,12 +700,16 @@ template <class T> class Processor {
case CycleReadFromS: throwaway_read(_s | 0x100); break;
case CycleReadFromPC: throwaway_read(_pc.full); break;
case CycleReadNMILow: read_mem(_pc.bytes.low, 0xfffa); break;
case CycleReadNMIHigh: read_mem(_pc.bytes.high, 0xfffb); break;
case CycleReadRSTLow: read_mem(_pc.bytes.low, 0xfffc); break;
case CycleReadRSTHigh: read_mem(_pc.bytes.high, 0xfffd); break;
case CycleSetIReadBRKLow: _interruptFlag = Flag::Interrupt; read_mem(_pc.bytes.low, 0xfffe); break;
case CycleReadBRKHigh: read_mem(_pc.bytes.high, 0xffff); break;
case OperationBRKPickVector:
// NMI can usurp BRK-vector operations
nextAddress.full = (_interrupt_requests & InterruptRequestFlags::NMI) ? 0xfffa : 0xfffe;
_interrupt_requests &= ~InterruptRequestFlags::NMI; // TODO: this probably doesn't happen now?
break;
case OperationNMIPickVector: nextAddress.full = 0xfffa; break;
case OperationRSTPickVector: nextAddress.full = 0xfffc; break;
case CycleReadVectorLow: read_mem(_pc.bytes.low, nextAddress.full); break;
case CycleReadVectorHigh: read_mem(_pc.bytes.high, nextAddress.full+1); break;
case OperationSetI: _interruptFlag = Flag::Interrupt; break;
case CyclePullPCL: _s++; read_mem(_pc.bytes.low, _s | 0x100); break;
case CyclePullPCH: _s++; read_mem(_pc.bytes.high, _s | 0x100); break;