3 files changed, 64 insertions, 28 deletions

diff --git a/gb.h b/gb.h
index ea092a2..15bd75e 100644
--- a/gb.h
+++ b/gb.h
@@ -40,6 +40,8 @@ typedef struct {
   void (*on_gpu_step)(const gb_t *);
   void (*on_gpu_set_mode)(const gb_t *, const uint8_t);
   void (*on_rst)(const gb_t *, const uint16_t);
+  void (*on_mmu_rb)(const gb_t *, const uint16_t, const uint8_t);
+  void (*on_mmu_wb)(const gb_t *, const uint16_t, const uint8_t);
   void *cb_data;
 } gb_config_t;
 
diff --git a/ops.yaml b/ops.yaml
index 199b61d..e3e7979 100644
--- a/ops.yaml
+++ b/ops.yaml
@@ -965,7 +965,7 @@ ops:
         h:
         c:
       code: |
-        cpu_ww(ctx, RW_HL, cpu_rw(ctx, RW_HL) - 1);
+        cpu_ww(ctx, RW_SP, cpu_rw(ctx, RW_SP) - 1);
     - id: INC A
       hex: 0x3C
       cat: "8-bit math"
@@ -8557,6 +8557,11 @@ templates:
     #define PORT_WY   0xFF4A
     #define PORT_WX   0xFF4B
 
+    // forward references for mmu_rp()/mmu_wp()
+    static void gpu_set_line(gb_t * const ctx, const uint8_t line);
+    static void gpu_set_mode(gb_t * const ctx, const uint8_t mode);
+    static bool gpu_is_active(const gb_t * const ctx);
+
     static uint8_t
     mmu_rp(
       const gb_t * const ctx,
@@ -8606,7 +8611,8 @@ templates:
       case PORT_STAT:
         return (ctx->gpu.stat & 0xF8) |
                ((ctx->gpu.line == ctx->gpu.lyc) ? (1 << 3) : 0) |
-               (ctx->gpu.mode & 0x3);
+               // always return mode 1 if lcd is disabled
+               (gpu_is_active(ctx) ? (ctx->gpu.mode & 0x3) : 1);
 
         break;
       case PORT_SCY:
@@ -8618,7 +8624,8 @@ templates:
 
         break;
       case PORT_LY:
-        return ctx->gpu.line;
+        // FIXME: is this correct?
+        return gpu_is_active(ctx) ? ctx->gpu.line : 144;
 
         break;
       case PORT_LYC:
@@ -8656,9 +8663,6 @@ templates:
       }
     }
 
-    // forward reference for mmu_wp()
-    static void gpu_set_line(gb_t * const ctx, const uint8_t line);
-
     static void
     mmu_wp(
       gb_t * const ctx,
@@ -8712,6 +8716,13 @@ templates:
       case PORT_LCDC:
         ctx->gpu.lcdc = val;
 
+        if (gpu_is_active(ctx)) {
+          // reset line, mode, and clock
+          gpu_set_line(ctx, 0);
+          gpu_set_mode(ctx, GPU_MODE_OAM);
+          ctx->gpu.clock = 0;
+        }
+
         break;
       case PORT_STAT:
         ctx->gpu.stat = (val & 0xF8);
@@ -8883,29 +8894,13 @@ templates:
       gb_t * const ctx,
       const uint16_t addr
     ) {
-      switch (addr & 0xF000) {
-      case 0x0000:
-      case 0x1000:
-      case 0x2000:
-      case 0x3000:
-      case 0x4000:
-      case 0x5000:
-      case 0x6000:
-      case 0x7000:
-        return rom_rb(ctx, addr);
-      case 0x8000:
-      case 0x9000:
-      case 0xA000:
-      case 0xB000:
-      case 0xC000:
-      case 0xD000:
-      case 0xE000:
-      case 0xF000:
-        return ram_rb(ctx, addr);
-      default:
-        // never reached
-        return 0;
+      const uint8_t val = (addr & 0x8000) ? ram_rb(ctx, addr) : rom_rb(ctx, addr);
+
+      if (ctx->config && ctx->config->on_mmu_rb) {
+        ctx->config->on_mmu_rb(ctx, addr, val);
       }
+
+      return val;
     }
 
     static void
@@ -9049,6 +9044,10 @@ templates:
       const uint16_t addr,
       const uint8_t val
     ) {
+      if (ctx->config && ctx->config->on_mmu_wb) {
+        ctx->config->on_mmu_wb(ctx, addr, val);
+      }
+
       switch (addr & 0xF000) {
       case 0x0000:
       case 0x1000:
@@ -10092,6 +10091,13 @@ templates:
       // TODO: implement DAA
     }
 
+    static bool
+    gpu_is_active(
+      const gb_t * const ctx
+    ) {
+      return ctx->gpu.lcdc & (1 << 7);
+    }
+
     static void
     gpu_set_line(
       gb_t * const ctx,
@@ -10250,6 +10256,10 @@ templates:
       gb_t * const ctx,
       const uint16_t clock
     ) {
+      if (!gpu_is_active(ctx)) {
+        return;
+      }
+
       // increment clock
       ctx->gpu.clock += clock;
 
diff --git a/test.c b/test.c
index 824458d..5900cf7 100644
--- a/test.c
+++ b/test.c
@@ -135,6 +135,28 @@ on_rst(
   printf("rst: addr = %04x\n", addr);
 }
 
+/* 
+ * static void
+ * on_mmu_rb(
+ *   const gb_t * const ctx,
+ *   const uint16_t addr,
+ *   const uint8_t val
+ * ) {
+ *   UNUSED(ctx);
+ *   printf("mmu_rb: addr = 0x%04X, val = 0x%02X\n", addr, val);
+ * }
+ */ 
+
+static void
+on_mmu_wb(
+  const gb_t * const ctx,
+  const uint16_t addr,
+  const uint8_t val
+) {
+  UNUSED(ctx);
+  printf("mmu_wb: addr = 0x%04X, val = 0x%02X\n", addr, val);
+}
+
 static const gb_config_t
 EXECUTE_CONFIG = {
   .on_set_rom_bank  = on_set_rom_bank,
@@ -146,6 +168,8 @@ EXECUTE_CONFIG = {
   .on_gpu_set_mode  = on_gpu_set_mode,
   .on_set_cpu_state = on_set_cpu_state,
   .on_rst           = on_rst,
+  // .on_mmu_rb        = on_mmu_rb,
+  .on_mmu_wb        = on_mmu_wb,
 };
 
 static void