Add notes for ring modulation (XORing)

src/engine/platform/pv1000.cpp

@@ -138,7 +138,7 @@ int DivPlatformPV1000::dispatch(DivCommand c) {
       chan[c.chan].pitch=c.value;
       chan[c.chan].freqChanged=true;
       break;
-    case DIV_CMD_WAVE:
+    case DIV_CMD_STD_NOISE_MODE: // ring modulation
       if (c.value&1) {
         rWrite(3,3);
       } else {

src/engine/platform/sound/d65modified.c

@@ -82,9 +82,9 @@ int d65010g031_square_tick(struct d65010g031_square_t *square, const int cycle)
 // this is the bit I altered
 // THIS IS **NOT** THE ORIGINAL SOFTWARE! I am plainly marking it as such!
 const int d65Volumes[3]={
-  3840,
-  5120,
-  8192
+  3840, // -6dB
+  5120, // -3dB
+  8192 // 0dB
 };
 
 int d65010g031_sound_tick(struct d65010g031_t *d65010g031, const int cycle)
@@ -96,7 +96,7 @@ int d65010g031_sound_tick(struct d65010g031_t *d65010g031, const int cycle)
 	}
 	if (d65010g031->ctrl & 2)
 	{
-		if (d65010g031->ctrl & 1)
+		if (d65010g031->ctrl & 1) // ring modulation
 		{
 			int sout[3] = {
 				d65010g031_square_tick(&d65010g031->square[0], cycle),

src/engine/sysDef.cpp

@@ -1842,7 +1842,7 @@ void DivEngine::registerSystems() {
     {DIV_INS_PV1000, DIV_INS_PV1000, DIV_INS_PV1000},
     {},
     {
-      {0x10, {DIV_CMD_WAVE, "10xx: Set waveform"}}
+      {0x10, {DIV_CMD_STD_NOISE_MODE, "10xx: Set ring modulation (0: disable, 1: enable)"}}
     }
   );