141 lines
3.9 KiB
D
141 lines
3.9 KiB
D
/+
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+ d6502/base.d
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+
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+ Copyright: 2007 Gerald Stocker
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+
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+ This file is part of Twoapple.
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+
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+ Twoapple is free software; you can redistribute it and/or modify
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+ it under the terms of the GNU General Public License as published by
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+ the Free Software Foundation; either version 2 of the License, or
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+ (at your option) any later version.
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+
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+ Twoapple is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ GNU General Public License for more details.
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+
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+ You should have received a copy of the GNU General Public License
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+ along with Twoapple; if not, write to the Free Software
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+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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+/
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module d6502.base;
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string hexByte(int decByte)
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{
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int highNybble = (decByte & 0xF0) >> 4;
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int lowNybble = decByte & 0x0F;
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string digits = "0123456789ABCDEF";
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return digits[highNybble..(highNybble + 1)] ~
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digits[lowNybble..(lowNybble + 1)];
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}
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final class StatusRegister
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{
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bool carry, decimal, interrupt, overflow;
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ubyte zero_, negative_;
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ubyte toByte()
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{
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return (carry ? 0x01 : 0) |
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((zero_ == 0) ? 0x02 : 0) |
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(interrupt ? 0x04 : 0) |
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(decimal ? 0x08 : 0) |
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0x30 | // break and reserved both set
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(overflow ? 0x40 : 0) |
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(negative_ & 0x80);
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}
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void fromByte(ubyte val)
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{
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carry = ((val & 0x01) != 0);
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zero_ = ((val & 0x02) ? 0 : 1);
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interrupt = ((val & 0x04) != 0);
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decimal = ((val & 0x08) != 0);
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overflow = ((val & 0x40) != 0);
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negative_ = val;
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}
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}
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class CpuBase
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{
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static string AbstractOpcodes()
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{
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string abstractOpcodes;
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for (int op = 0; op < 256; ++op)
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abstractOpcodes ~= "abstract void opcode" ~ hexByte(op) ~ "();\n";
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return abstractOpcodes;
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}
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mixin(AbstractOpcodes());
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ushort programCounter;
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ubyte accumulator, xIndex, yIndex, stackPointer;
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final StatusRegister flag;
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bool signalActive, irqActive, resetActive, nmiActive, nmiArmed;
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ushort opcodePC;
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ubyte opcode, operand1, operand2;
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final ubyte[] save()
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{
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ubyte[] data = new ubyte[12];
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data[0] = programCounter & 0xFF;
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data[1] = programCounter >> 8;
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data[2] = accumulator;
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data[3] = xIndex;
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data[4] = yIndex;
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data[5] = stackPointer;
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data[6] = flag.toByte();
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data[7] = (signalActive ? 1 : 0);
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data[8] = (irqActive ? 1 : 0);
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data[9] = (resetActive ? 1 : 0);
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data[10] = (nmiActive ? 1 : 0);
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data[11] = (nmiArmed ? 1 : 0);
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return data;
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}
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final void restore(ubyte[] data)
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{
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assert (data.length >= 12);
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programCounter = data[0] | (data[1] << 8);
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accumulator = data[2];
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xIndex = data[3];
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yIndex = data[4];
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stackPointer = data[5];
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flag.fromByte(data[6]);
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signalActive = ((data[7] == 0) ? false : true);
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irqActive = ((data[8] == 0) ? false : true);
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resetActive = ((data[9] == 0) ? false : true);
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nmiActive = ((data[10] == 0) ? false : true);
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nmiArmed = ((data[11] == 0) ? false : true);
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}
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final void reboot()
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{
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restore([0, 0, 0, 0, 0, 0xFF, 0, 0, 0, 0, 0, 1]);
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}
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ubyte delegate(ushort addr) memoryRead;
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void delegate(ushort addr, ubyte val) memoryWrite;
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debug(disassemble)
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{
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string delegate(ushort addr) memoryName;
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}
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version(CycleAccuracy) void delegate() tick;
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version(CumulativeCycles) void delegate(int cycles) ticks;
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abstract void run(bool continuous);
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abstract void stop();
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version(CycleAccuracy) abstract bool checkFinalCycle();
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abstract void resetLow();
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abstract void nmiLow(bool signalLow);
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abstract void irqLow(bool signalLow);
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}
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