public release of panzgb

2025-11-24 13:37:49 +01:00
commit d08fbfe1aa
18 changed files with 3827 additions and 0 deletions
--- a/lib/gc-interrupts.c
+++ b/lib/gc-interrupts.c
@@ -0,0 +1,76 @@
+#include "gb-impl.h"
+
+void setTimerFreq(gb *cpu) {
+    BYTE freq = readMemory(cpu, TIMER_CONTROLLER) & 0x3;
+    switch (freq) {
+    case 0:
+        cpu->clockBeforeTimer = 1024;
+        break; // freq 4096
+    case 1:
+        cpu->clockBeforeTimer = 16;
+        break; // freq 262144
+    case 2:
+        cpu->clockBeforeTimer = 64;
+        break; // freq 65536
+    case 3:
+        cpu->clockBeforeTimer = 256;
+        break; // freq 16382
+    }
+}
+
+void increaseTimer(gb *cpu, BYTE clocks) {
+    //Handle divider timer
+    cpu->clockBeforeDividerTimer -= clocks;
+    if (cpu->clockBeforeDividerTimer <= 0) {
+        cpu->clockBeforeDividerTimer += 255;
+        cpu->memory[DIVIDER_TIMER]++;
+    }
+    /*Timer is enabled ?*/
+    if ((readMemory(cpu, TIMER_CONTROLLER) & 0x4) != 0) {
+        cpu->clockBeforeTimer -= clocks;
+        if (cpu->clockBeforeTimer <= 0) {
+            BYTE currentTimer = readMemory(cpu, TIMER_ADDR);
+
+            setTimerFreq(cpu);
+            writeMemory(cpu, TIMER_ADDR, currentTimer + 1);
+            /*The timer should overflow ?*/
+            if (currentTimer == 255) {
+                writeMemory(cpu, TIMER_ADDR, readMemory(cpu, TIMER_DEFAULT));
+                raiseInterrupt(cpu, 2);
+            }
+        }
+    }
+}
+
+void raiseInterrupt(gb *cpu, BYTE code) {
+    BYTE interruptRequest = readMemory(cpu, INTERRUPT_REQUEST_ADDR);
+    interruptRequest |= (0x1 << code);
+    writeMemory(cpu, INTERRUPT_REQUEST_ADDR, interruptRequest);
+    cpu->cpuHalted = 1;
+}
+
+void handleInterrupts(gb *cpu) {
+    BYTE req = readMemory(cpu, INTERRUPT_REQUEST_ADDR);
+    BYTE enabled = readMemory(cpu, INTERRUPT_ENABLED_ADDR);
+
+    BYTE mask = req & enabled;
+
+    if (cpu->master_interr_switch != 0 && mask != 0) {
+        /*Interrupts are enabled and an interrupt is set, let's raise it */
+        for (BYTE i = 0; i < 5; i++) {
+            if ((mask & (0x1 << i)) != 0) {
+                //Disable other interrupts
+                cpu->master_interr_switch = 0;
+                //Mark interrupt as handled
+                req &= ~(0x1 << i);
+                writeMemory(cpu, INTERRUPT_REQUEST_ADDR, req);
+
+                WORD currentPC = cpu->progCounter;
+                PUSH(cpu, cpu->stack, currentPC);
+                //Which routine should we use?
+                cpu->progCounter = 0x40 + (i<<3);
+                return;
+            }
+        }
+    }
+}