Dave Van Wagner
6502 emulator for Commodore 64 ROMs, serial terminal edition for MBED. Recommend terminal echo on, line edit on, caps lock, 115200bps, implicit carriage return on newline, currently non-buffered so don't paste lots of stuff
More details at:
[https://github.com/davervw] [https://techwithdave.davevw.com/2020/03/simple-emu-c64.html]
Diff: emu6502.cpp
- Revision:
- 4:0461c100cbbb
- Parent:
- 0:90de1cbc8a5f
- Child:
- 7:f49fa56672d8
--- a/emu6502.cpp Fri Apr 10 04:32:54 2020 +0000
+++ b/emu6502.cpp Sun Apr 12 19:26:44 2020 +0000
@@ -11,7 +11,6 @@
// davevw.com
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
-//
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
@@ -55,6 +54,8 @@
bool trace = false;
bool step = false;
+#define USE_IRQ 0
+
extern void ResetRun(bool (*ExecutePatch)(void))
{
ushort addr = (ushort)((GetMemory(0xFFFC) | (GetMemory(0xFFFD) << 8))); // RESET vector
@@ -98,9 +99,9 @@
static void BRK(byte *p_bytes)
{
++PC;
- PHP();
Push(HI(PC));
Push(LO(PC));
+ PHP();
B = true;
PC = (ushort)(GetMemory(0xFFFE) + (GetMemory(0xFFFF) << 8));
*p_bytes = 0;
@@ -186,7 +187,7 @@
}
}
-static void ADC(byte value)
+static void ADC_OP(byte value)
{
int result;
if (D)
@@ -228,7 +229,7 @@
SetA(A & value);
}
-static void BIT(byte value)
+static void BIT_OP(byte value)
{
Z = (A & value) == 0;
N = (value & 0x80) != 0;
@@ -491,8 +492,8 @@
static void RTI(ushort *p_addr, byte *p_bytes)
{
PLP();
+ byte lo = Pop();
byte hi = Pop();
- byte lo = Pop();
*p_bytes = 0; // make sure caller does not increase addr by one
*p_addr = (ushort)((hi << 8) | lo);
}
@@ -660,39 +661,60 @@
bool conditional;
byte bytes;
+#if (USE_IRQ == 1)
+ // IRQ support
+ Timer timer;
+ const double interrupt_time = 1.0 / 60.0 ; // 60 times per second
+ timer.start();
+ double timer_then = timer.read();
+#endif
+
PC = addr;
while (true)
{
while (true)
{
- bytes = 1;
- //bool breakpoint = false;
- //if (Breakpoints.Contains(PC))
- // breakpoint = true;
- bool breakpoint = (addr == 0xFD88);
- if (trace || breakpoint || step)
+#if (USE_IRQ == 1)
+ if (!I && (timer.read()-timer_then) >= interrupt_time) // IRQ
+ {
+ timer_then = timer.read(); // reset timer
+ Push(HI(PC));
+ Push(LO(PC));
+ PHP();
+ I = true;
+ PC = (GetMemory(0xfffe) | (GetMemory(0xffff) << 8));
+ }
+ else
+#endif
{
- ushort addr2;
- char line[27];
- char dis[13];
- DisassembleLong(PC, &conditional, &bytes, &addr2, dis, sizeof(dis), line, sizeof(line));
- char state[33];
- GetDisplayState(state, sizeof(state));
- char full_line[80];
- snprintf(full_line, sizeof(full_line), "%-30s%s\n", line, state);
-#ifdef WIN32
- OutputDebugStringA(full_line);
-#else
- pc.printf("%s", full_line);
-#endif
- if (step)
- step = step; // user can put debug breakpoint here to allow stepping
- if (breakpoint)
- breakpoint = breakpoint; // user can put debug breakpoint here to allow break
+ bytes = 1;
+ bool breakpoint = false;
+ //if (Breakpoints.Contains(PC))
+ // breakpoint = true;
+ if (trace || breakpoint || step)
+ {
+ ushort addr2;
+ char line[27];
+ char dis[13];
+ DisassembleLong(PC, &conditional, &bytes, &addr2, dis, sizeof(dis), line, sizeof(line));
+ char state[33];
+ GetDisplayState(state, sizeof(state));
+ char full_line[80];
+ snprintf(full_line, sizeof(full_line), "%-30s%s\n", line, state);
+ #ifdef WIN32
+ OutputDebugStringA(full_line);
+ #else
+ pc.printf("%s", full_line);
+ #endif
+ if (step)
+ step = step; // user can put debug breakpoint here to allow stepping
+ if (breakpoint)
+ breakpoint = breakpoint; // user can put debug breakpoint here to allow break
+ }
+ if (ExecutePatch != 0 && !ExecutePatch()) // allow execute to be overriden at a specific address
+ break;
}
- if (ExecutePatch != 0 && !ExecutePatch()) // allow execute to be overriden at a specific address
- break;
}
switch (GetMemory(PC))
@@ -718,13 +740,13 @@
case 0x20: JSR(&PC, &bytes); break;
case 0x21: AND(GetIndX(PC, &bytes)); break;
- case 0x24: BIT(GetZP(PC, &bytes)); break;
+ case 0x24: BIT_OP(GetZP(PC, &bytes)); break;
case 0x25: AND(GetZP(PC, &bytes)); break;
case 0x26: SetZP(ROL(GetZP(PC, &bytes)), PC, &bytes); break;
case 0x28: PLP(); break;
case 0x29: AND(GetIM(PC, &bytes)); break;
case 0x2A: SetA(ROL(A)); break;
- case 0x2C: BIT(GetABS(PC, &bytes)); break;
+ case 0x2C: BIT_OP(GetABS(PC, &bytes)); break;
case 0x2D: AND(GetABS(PC, &bytes)); break;
case 0x2E: ROL(GetABS(PC, &bytes)); break;
@@ -758,23 +780,23 @@
case 0x5E: SetABSX(LSR(GetABSX(PC, &bytes)), PC, &bytes); break;
case 0x60: RTS(&PC, &bytes); break;
- case 0x61: ADC(GetIndX(PC, &bytes)); break;
- case 0x65: ADC(GetZP(PC, &bytes)); break;
+ case 0x61: ADC_OP(GetIndX(PC, &bytes)); break;
+ case 0x65: ADC_OP(GetZP(PC, &bytes)); break;
case 0x66: SetZP(ROR(GetZP(PC, &bytes)), PC, &bytes); break;
case 0x68: PLA(); break;
- case 0x69: ADC(GetIM(PC, &bytes)); break;
+ case 0x69: ADC_OP(GetIM(PC, &bytes)); break;
case 0x6A: SetA(ROR(A)); break;
case 0x6C: JMPIND(&PC, &bytes); break;
- case 0x6D: ADC(GetABS(PC, &bytes)); break;
+ case 0x6D: ADC_OP(GetABS(PC, &bytes)); break;
case 0x6E: SetABS(ROR(GetABS(PC, &bytes)), PC, &bytes); break;
case 0x70: BVS(&PC, &conditional, &bytes); break;
- case 0x71: ADC(GetIndY(PC, &bytes)); break;
- case 0x75: ADC(GetZPX(PC, &bytes)); break;
+ case 0x71: ADC_OP(GetIndY(PC, &bytes)); break;
+ case 0x75: ADC_OP(GetZPX(PC, &bytes)); break;
case 0x76: SetZPX(ROR(GetZPX(PC, &bytes)), PC, &bytes); break;
case 0x78: SEI(); break;
- case 0x79: ADC(GetABSY(PC, &bytes)); break;
- case 0x7D: ADC(GetABSX(PC, &bytes)); break;
+ case 0x79: ADC_OP(GetABSY(PC, &bytes)); break;
+ case 0x7D: ADC_OP(GetABSX(PC, &bytes)); break;
case 0x7E: SetABSX(ROR(GetABSX(PC, &bytes)), PC, &bytes); break;
case 0x81: SetIndX(A, PC, &bytes); break;