wram analysis

snes/wram/PPU.c

@@ -0,0 +1,90 @@
+#include "data.h"
+
+byte tileMapLocation[4];
+word characterLocation[4];
+
+void waitForVBlank(void)
+{
+    byte Status;
+    do {
+        Status = *(byte *) 0x4210;
+    } while (!(Status & 0x80));
+}
+
+void setTileMapLocation(word vramDst, byte screenProp, byte bgNumber)
+{
+    tileMapLocation[bgNumber] = ((vramDst >> 8) & 0xfc) | (screenProp & 0x03);
+    *(byte *) (0x2107 + bgNumber) = tileMapLocation[bgNumber];
+}
+
+void restoreTileMapLocation(byte bgNumber)
+{
+    *(byte *) (0x2107 + bgNumber) = tileMapLocation[bgNumber];
+}
+
+void setCharacterLocation(word vramDst, byte bgNumber)
+{
+    characterLocation[bgNumber] = vramDst;
+    if (bgNumber < 2) {
+        *(byte *) 0x210b =
+            (characterLocation[1] >> 8 & 0xf0) + (characterLocation[0] >> 12);
+    } else {
+        *(byte *) 0x210c =
+            (characterLocation[3] >> 8 & 0xf0) + (characterLocation[2] >> 12);
+    }
+}
+
+void restoreCharacterLocation(byte bgNumber)
+{
+    setCharacterLocation(characterLocation[bgNumber], bgNumber);
+}
+
+void VRAMByteWrite(byte value, word vramDst)
+{
+    *(byte *) 0x2115 = 0x80;
+    *(word *) 0x2116 = vramDst;
+
+    *(byte *) 0x2118 = value;
+}
+
+void VRAMLoad(word src, word vramDst, word size)
+{
+    // set address in VRam for read or write ($2116) + block size transfer ($2115)
+    *(byte *) 0x2115 = 0x80;
+    *(word *) 0x2116 = vramDst;
+
+    *(word *) 0x4300 = 0x1801;  // set DMA control register (1 word inc) 
+    // and destination ($21xx xx -> 0x18)
+    *(word *) 0x4302 = src;     // DMA channel x source address offset 
+    // (low $4302 and high $4303 optimisation)
+    *(byte *) 0x4304 = 0x01;    // DMA channel x source address bank
+    *(word *) 0x4305 = size;    // DMA channel x transfer size 
+    // (low $4305 and high $4306 optimisation)
+
+    // Turn on DMA transfer for this channel
+    waitForVBlank();
+    *(byte *) 0x2100 = 0x80;
+    *(byte *) 0x420b = 0x01;
+    *(byte *) 0x2100 = 0x00;
+}
+
+void CGRAMLoad(word src, byte cgramDst, word size)
+{
+
+    // set address in VRam for read or write + block size
+    *(byte *) 0x2121 = cgramDst;
+
+    *(word *) 0x4300 = 0x2200;  // set DMA control register (1 byte inc) 
+    // and destination ($21xx xx -> 022)
+    *(word *) 0x4302 = src;     // DMA channel x source address offset
+    // (low $4302 and high $4303 optimisation)
+    *(byte *) 0x4304 = 0x01;    // DMA channel x source address bank
+    *(word *) 0x4305 = size;    // DMA channel x transfer size
+    // (low $4305 and high $4306 optimisation)
+
+    // Turn on DMA transfer for this channel
+    waitForVBlank();
+    *(byte *) 0x2100 = 0x80;
+    *(byte *) 0x420b = 0x01;
+    *(byte *) 0x2100 = 0x00;
+}