Direct access to IF register (#20)

kremi151 · Aug 12, 2020 · 3b1bc36 · 3b1bc36
1 parent 44d0ef5
commit 3b1bc36
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Showing 3 changed files with 11 additions and 5 deletions.
diff --git a/core/source/emulator/cpu.cpp b/core/source/emulator/cpu.cpp
@@ -267,7 +267,8 @@ bool CPU::doInterrupts() {
     if (instrContext.cpuState == CPUState::STOPPED) {
         return false;
     }
-    u8 _if = memory->read8BitsAt(FB_REG_IF) & 0x1fu;
+    u8 &_if = ioRegisters.getIF();
+    _if %= 0x1fu;
     u8 _ie = memory->read8BitsAt(FB_REG_IE) & 0x1fu;
     u8 _intr = _if & _ie & 0x1f;
     if (!_intr) {
@@ -294,8 +295,7 @@ bool CPU::doInterrupts() {
 
         instrContext.progCounter = addr;
         debug_print_4("Do interrupt at 0x%04X\n", addr);
-        _if &= ~bitMask;
-        memory->write8BitsTo(FB_REG_IF, _if); // TODO: Investigate "Timer doesn't work" error from ROM output
+        _if &= ~bitMask; // Writes directly to io_registry
         // TODO: Interrupt Service Routine should take 5 cycles
         return true;
     }
@@ -373,8 +373,8 @@ void CPU::doTimers(u8 clocks) {
 
 void CPU::requestInterrupt(InterruptType type) {
     //fprintf(stdout, "#req int %d\n", type);
-    u8 _if = memory->read8BitsAt(FB_REG_IF);
-    memory->write8BitsTo(FB_REG_IF, _if | getInterruptBitMask(type));
+    u8 &_if = ioRegisters.getIF();
+    _if |= getInterruptBitMask(type);
 }
 
 void CPU::setProgramCounter(u16 offset) {

diff --git a/core/source/emulator/io_registers.cpp b/core/source/emulator/io_registers.cpp
@@ -20,6 +20,7 @@ using namespace FunkyBoy;
 
 #define FB_REG_OFFSET_P1 (FB_REG_P1 - 0xFF00)
 #define FB_REG_OFFSET_DIV (FB_REG_DIV - 0xFF00)
+#define FB_REG_OFFSET_IF (FB_REG_IF - 0xFF00)
 #define FB_REG_OFFSET_STAT (FB_REG_STAT - 0xFF00)
 #define FB_REG_OFFSET_LY (FB_REG_LY - 0xFF00)
 
@@ -155,4 +156,8 @@ void io_registers::updateLCD(bool lcdOn, GPUMode gpuMode, u8 ly) {
 
 u8 &io_registers::getP1() {
     return *(hwIO + FB_REG_OFFSET_P1);
+}
+
+u8 &io_registers::getIF() {
+    return *(hwIO + FB_REG_OFFSET_IF);
 }
diff --git a/core/source/emulator/io_registers.h b/core/source/emulator/io_registers.h
@@ -72,6 +72,7 @@ namespace FunkyBoy {
         void updateLCD(bool lcdOn, GPUMode gpuMode, u8 ly);
 
         u8 &getP1();
+        u8 &getIF();
 
         friend class CPU;
     };