[Core/VDP] fixed spurious 8K-16K VRAM switching when reloading SG-1000 context + minor optimizations

core/vdp_ctrl.c

@@ -5,7 +5,7 @@
  *  Support for SG-1000 (TMS99xx & 315-5066), Master System (315-5124 & 315-5246), Game Gear & Mega Drive VDP
  *
  *  Copyright (C) 1998-2003  Charles Mac Donald (original code)
- *  Copyright (C) 2007-2015  Eke-Eke (Genesis Plus GX)
+ *  Copyright (C) 2007-2016  Eke-Eke (Genesis Plus GX)
  *
  *  Redistribution and use of this code or any derivative works are permitted
  *  provided that the following conditions are met:
@@ -180,6 +180,26 @@ static void (*const dma_func[16])(unsigned int length) =
   vdp_dma_copy,vdp_dma_copy,vdp_dma_copy,vdp_dma_copy
 };
 
+/* BG rendering functions */
+static void (*const render_bg_modes[16])(int line) =
+{
+  render_bg_m0,   /* Graphics I */
+  render_bg_m2,   /* Graphics II */
+  render_bg_m4,   /* Mode 4 */
+  render_bg_m4,   /* Mode 4 */
+  render_bg_m3,   /* Multicolor */
+  render_bg_m3x,  /* Multicolor (Extended PG) */
+  render_bg_m4,   /* Mode 4 */
+  render_bg_m4,   /* Mode 4 */
+  render_bg_m1,   /* Text */
+  render_bg_m1x,  /* Text (Extended PG) */
+  render_bg_m4,   /* Mode 4 */
+  render_bg_m4,   /* Mode 4 */
+  render_bg_inv,  /* Invalid (1+3) */
+  render_bg_inv,  /* Invalid (1+2+3) */
+  render_bg_m4,   /* Mode 4 */
+  render_bg_m4,   /* Mode 4 */
+};
 
 /*--------------------------------------------------------------------------*/
 /* Init, reset, context functions                                           */
@@ -451,12 +471,14 @@ int vdp_context_load(uint8 *state)
     }
     else
     {
+      /* TMS-99xx registers are updated directly to prevent spurious 4K->16K VRAM switching */
       for (i=0;i<0x08;i++) 
       {
-        pending = 1;
+        reg[i] = temp_reg[i];
-        addr_latch = temp_reg[i];
-        vdp_tms_ctrl_w(0x80 | i);
       }
+
+      /* Rendering mode */
+      render_bg = render_bg_modes[((reg[0] & 0x02) | (reg[1] & 0x18)) >> 1];
     }
   }
   else
@@ -517,7 +539,7 @@ int vdp_context_load(uint8 *state)
     color_update_m4(0x40, *(uint16 *)&cram[(0x10 | (border & 0x0F)) << 1]);
   }
 
-  /* invalidate cache */
+  /* invalidate tile cache */
   for (i=0;i<bg_list_index;i++) 
   {
     bg_name_list[i]=i;
@@ -534,7 +556,7 @@ int vdp_context_load(uint8 *state)
 
 void vdp_dma_update(unsigned int cycles)
 {
-  int dma_cycles, dma_bytes;
+  unsigned int dma_cycles, dma_bytes;
 
   /* DMA transfer rate (bytes per line) 
 
@@ -619,7 +641,7 @@ void vdp_dma_update(unsigned int cycles)
   }
 
   /* Process DMA */
-  if (dma_bytes > 0)
+  if (dma_bytes)
   {
     /* Update DMA length */
     dma_length -= dma_bytes;
@@ -1006,62 +1028,7 @@ void vdp_sms_ctrl_w(unsigned int data)
         }
 
         /* Rendering mode */
-        switch (mode)
+        render_bg = render_bg_modes[mode>>1];
-        {
-          case 0x00: /* Graphics I */
-          {
-            render_bg = render_bg_m0;
-            break;
-          }
-
-          case 0x10: /* Text */
-          {
-            render_bg = render_bg_m1;
-           break;
-          }
-
-          case 0x02: /* Graphics II */
-          {
-            render_bg = render_bg_m2;
-            break;
-          }
-
-          case 0x12: /* Text (Extended PG) */
-          {
-            render_bg = render_bg_m1x;
-            break;
-          }
-
-          case 0x08: /* Multicolor */
-          {
-            render_bg = render_bg_m3;
-            break;
-          }
-
-          case 0x18: /* Invalid (1+3) */
-          {
-            render_bg = render_bg_inv;
-            break;
-          }
-
-          case 0x0A: /* Multicolor (Extended PG) */
-          {
-            render_bg = render_bg_m3x;
-            break;
-          }
-
-          case 0x1A: /* Invalid (1+2+3) */
-          {
-            render_bg = render_bg_inv;
-           break;
-          }
-
-          default: /* Mode 4 */
-          {
-            render_bg = render_bg_m4;
-            break;
-          }
-        }
 
         /* Mode switching */
         if (prev & 0x04)
@@ -1140,59 +1107,8 @@ void vdp_tms_ctrl_w(unsigned int data)
       /* Check VDP mode changes */
       if (data < 2)
       {
-        int mode = (reg[0] & 0x02) | (reg[1] & 0x18);
-
         /* Rendering mode */
-        switch (mode)
+        render_bg = render_bg_modes[((reg[0] & 0x02) | (reg[1] & 0x18)) >> 1];
-        {
-          case 0x00: /* Graphics I */
-          {
-            render_bg = render_bg_m0;
-            break;
-          }
-
-          case 0x10: /* Text */
-          {
-            render_bg = render_bg_m1;
-            break;
-          }
-
-          case 0x02: /* Graphics II */
-          {
-            render_bg = render_bg_m2;
-            break;
-          }
-
-          case 0x12: /* Text (Extended PG) */
-          {
-            render_bg = render_bg_m1x;
-            break;
-          }
-
-          case 0x08: /* Multicolor */
-          {
-            render_bg = render_bg_m3;
-            break;
-          }
-
-          case 0x18: /* Invalid (1+3) */
-          {
-            render_bg = render_bg_inv;
-            break;
-          }
-
-          case 0x0A: /* Multicolor (Extended PG) */
-          {
-            render_bg = render_bg_m3x;
-            break;
-          }
-
-          case 0x1A: /* Invalid (1+2+3) */
-          {
-            render_bg = render_bg_inv;
-            break;
-          }
-        }
       }
     }
   }

core/vdp_ctrl.h

@@ -5,7 +5,7 @@
  *  Support for SG-1000 (TMS99xx & 315-5066), Master System (315-5124 & 315-5246), Game Gear & Mega Drive VDP
  *
  *  Copyright (C) 1998-2003  Charles Mac Donald (original code)
- *  Copyright (C) 2007-2015  Eke-Eke (Genesis Plus GX)
+ *  Copyright (C) 2007-2016  Eke-Eke (Genesis Plus GX)
  *
  *  Redistribution and use of this code or any derivative works are permitted
  *  provided that the following conditions are met: