Adjust GAMESTART logic, consolidate VIP sign-extensions

core/bus.c

@@ -159,6 +159,8 @@ static void busRead(VB *sim, uint32_t address, int type, int32_t *value) {
 
         case 2: /* Misc. I/O */
             *value = busReadMisc(sim, address, type);
+            if (type == VB_S8)
+                *value = (int8_t) *value;
             break;
 
         case 3: break; /* Unmapped */

core/vb.c

@@ -312,6 +312,7 @@ struct VB {
             int      frame;    /* FRMCYC counter */
             int32_t  halfword; /* Current output halfword offset */
             int      step;     /* Processing phase */
+            uint8_t  toggle;   /* Switch frame buffers next frame */
             uint32_t until;    /* Clocks until interrupt condition */
         } xp;
 
@@ -326,6 +327,7 @@ struct VB {
         uint16_t spt[4];     /* Object control */
 
         /* Rendering shadow memory */
+        uint8_t  buffer;            /* Output buffer */
         uint16_t halfwords[384*28]; /* Output timing by 1x8 halfword */
         Pixels   output[2];         /* Output images, row-major */
         Pixels   shadow;            /* Drawing shadow image, column-major */
@@ -632,7 +634,7 @@ VBAPI void vbGetPixels(VB *sim, void *left, int leftStrideX, int leftStrideY,
             continue;
 
         /* Transfer pixels to the destination */
-        src = sim->vip.output[sim->vip.dp.buffer ^ 1][i];
+        src = sim->vip.output[sim->vip.buffer][i];
         for (y = 0; y < 224; y++, dest += yStride)
         for (x = offset = 0; x < 384; x++, offset += xStride)
             dest[offset] = *src++;

core/vb.h

@@ -126,7 +126,6 @@ typedef int  (*vbOnWrite    )(VB *sim, uint32_t address, int type, int32_t *valu
 
 VBAPI int           vbEmulate             (VB *sim, uint32_t *clocks);
 VBAPI int           vbEmulateEx           (VB **sims, unsigned count, uint32_t *clocks);
-VBAPI void*         vbGetCallback         (VB *sim, int id);
 VBAPI void*         vbGetCartRAM          (VB *sim, uint32_t *size);
 VBAPI void*         vbGetCartROM          (VB *sim, uint32_t *size);
 VBAPI vbOnException vbGetExceptionCallback(VB *sim);

core/vip.c

@@ -598,7 +598,7 @@ static void vipTransferColumn(VB *sim, int32_t eye) {
 
     /* Select destination address in host memory */
     dest = &sim->vip.output
-        [sim->vip.dp.buffer][eye][sim->vip.dp.column];
+        [sim->vip.buffer ^ 1][eye][sim->vip.dp.column];
 
     /* Output is disabled */
     if (!sim->vip.dp.enabled) {
@@ -654,28 +654,29 @@ static int vipEmulateDisplay(VB *sim, uint32_t clocks) {
                 vipThrow(sim, 0x0010); /* FRAMESTART */
 
                 /* Game frame */
-                if (sim->vip.xp.xpen) {
                 if (sim->vip.xp.frame >= sim->vip.frmcyc) {
                     sim->vip.xp.frame = 0;
 
-                        /* Initiate drawing procedure */
-                        if (sim->vip.xp.step == 0) {
-                            sim->vip.dp.buffer  ^= 1;
-                            sim->vip.xp.enabled  = 1;
-                            sim->vip.xp.overtime = 0;
-                            sim->vip.xp.step     = 1;
                     vipThrow(sim, 0x0008); /* GAMESTART */
-                        }
-
-                        /* Drawing procedure has run into overtime */
-                        else {
+                    if (sim->vip.xp.step != 0) {
                         sim->vip.xp.overtime = 1;
                         vipThrow(sim, 0x8000); /* TIMEERR */
                     }
 
-                    } else sim->vip.xp.frame++;
+                    /* Initiate drawing procedure */
+                    else if (sim->vip.xp.xpen) {
+                        sim->vip.dp.buffer  ^= sim->vip.xp.toggle;
+                        sim->vip.xp.enabled  = 1;
+                        sim->vip.xp.overtime = 0;
+                        sim->vip.xp.step     = 1;
+                        sim->vip.xp.toggle   = 0;
                     }
 
+                }
+
+                /* Not a game frame */
+                else sim->vip.xp.frame++;
+
                 break;
 
             /* 0ms-3ms - Idle */
@@ -767,6 +768,7 @@ static int vipEmulateDisplay(VB *sim, uint32_t clocks) {
             /* 18ms-20ms - Idle */
 
             case 8: /* 20ms - Display interval complete */
+                sim->vip.buffer ^= 1;
                 sim->vip.dp.step = 0;
                 if (vipOnFrame(sim))
                     return 1;
@@ -1264,6 +1266,7 @@ static void vipEmulateDrawing(VB *sim, uint32_t clocks) {
             case 4: /* Drawing complete */
                 sim->vip.xp.enabled = 0;
                 sim->vip.xp.step    = 0;
+                sim->vip.xp.toggle  = 1;
                 if (sim->vip.dp.buffer == 0)
                      sim->vip.xp.f1bsy = 0;
                 else sim->vip.xp.f0bsy = 0;
@@ -1313,8 +1316,13 @@ static void vipRead(VB *sim, uint32_t address, int type, int32_t *value) {
         *value = 0;
 
     /* I/O register */
-    else if (address < 0x60000)
+    else if (address < 0x60000) {
         *value = vipReadIO(sim, address, type);
+        switch (type) {
+            case VB_S8 : *value = (int8_t ) *value; break;
+            case VB_S16: *value = (int16_t) *value; break;
+        }
+    }
 
     /* Unmapped */
     else if (address < 0x78000)
@@ -1334,7 +1342,7 @@ static void vipReset(VB *sim) {
     Character *chr;     /* Character state */
     Object    *obj;     /* Object state */
     World     *world;   /* World state */
-    int        x, y;  /* Iterators */
+    int        x, y, z; /* Iterators */
 
     /* Normal */
     sim->vip.intenb   = 0x0000;
@@ -1424,6 +1432,13 @@ static void vipReset(VB *sim) {
     sim->vip.xp.sbcount  = 0;
     sim->vip.xp.sbout    = 0;
 
+    /* Other */
+    sim->vip.buffer = 0;
+    for (x = 0; x < 2; x++)
+    for (y = 0; y < 2; y++)
+    for (z = 0; z < 384*224; z++)
+        sim->vip.output[x][y][z] = 0;
+
     /* Display processor other */
     sim->vip.dp.brt[0] = 0;
     sim->vip.dp.buffer = 0; /* TODO: Hardware might actually do this */
@@ -1434,6 +1449,7 @@ static void vipReset(VB *sim) {
     /* Pixel processor other */
     sim->vip.xp.clocks = 0;
     sim->vip.xp.step   = 0;
+    sim->vip.xp.toggle = 0;
     sim->vip.xp.until  = 0;
 }