From b4a7f0f5b7447e5127b65f025102c2452be3a00a Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Fri, 3 Jun 2022 16:13:57 -0500
Subject: [PATCH] YM2612: - C   S   M -

CSM only available with Nuked core
may not work on VGM export if you compress VGM (removes timer A writes)
---
 TODO.md                            |  2 --
 src/engine/platform/genesis.cpp    | 22 -------------------
 src/engine/platform/genesisext.cpp | 35 ++++++++++++++++++++++++++++++
 3 files changed, 35 insertions(+), 24 deletions(-)

diff --git a/TODO.md b/TODO.md
index c5c1ca0e0..2dc7bb8ef 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,7 +1,5 @@
 # to-do for 0.6pre1
 
-- additional YM2612 features
-  - CSM
 - MSM6258 pitch and clock select
 - Game Boy envelope macro/sequence
 - rewrite the system name detection function anyway
diff --git a/src/engine/platform/genesis.cpp b/src/engine/platform/genesis.cpp
index f240997cd..2368fc0b5 100644
--- a/src/engine/platform/genesis.cpp
+++ b/src/engine/platform/genesis.cpp
@@ -512,28 +512,6 @@ void DivPlatformGenesis::tick(bool sysTick) {
     }
   }
 
-  if (extMode && softPCM) {
-    if (chan[7].freqChanged) {
-      chan[7].freq=parent->calcFreq(chan[7].baseFreq,chan[7].pitch,true,0,chan[7].pitch2,chipClock,CHIP_DIVIDER);
-      int wf=0x400-chan[7].freq;
-      printf("freq: %d\n",wf);
-      immWrite(0x24,wf>>2);
-      immWrite(0x25,wf&3);
-      chan[7].freqChanged=false;
-    }
-
-    if (chan[7].keyOn) {
-      printf("CSM key on\n");
-      immWrite(0x27,0x81);
-      chan[7].keyOn=false;
-    }
-    if (chan[7].keyOff) {
-      printf("CSM key off\n");
-      immWrite(0x27,0x40);
-      chan[7].keyOff=false;
-    }
-  }
-
   for (int i=0; i<7; i++) {
     if (i==2 && extMode) continue;
     if (chan[i].freqChanged) {
diff --git a/src/engine/platform/genesisext.cpp b/src/engine/platform/genesisext.cpp
index 8b4629b94..e105f5604 100644
--- a/src/engine/platform/genesisext.cpp
+++ b/src/engine/platform/genesisext.cpp
@@ -23,6 +23,7 @@
 
 #include "genesisshared.h"
 
+#define CHIP_DIVIDER 72
 #define CHIP_FREQBASE 9440540
 
 int DivPlatformGenesisExt::dispatch(DivCommand c) {
@@ -446,9 +447,43 @@ void DivPlatformGenesisExt::tick(bool sysTick) {
       opChan[i].keyOn=false;
     }
   }
+
+  if (extMode && softPCM) {
+    if (chan[7].freqChanged) {
+      chan[7].freq=parent->calcFreq(chan[7].baseFreq,chan[7].pitch,true,0,chan[7].pitch2,chipClock,CHIP_DIVIDER);
+      if (chan[7].freq<1) chan[7].freq=1;
+      if (chan[7].freq>1024) chan[7].freq=1024;
+      int wf=0x400-chan[7].freq;
+      immWrite(0x24,wf>>2);
+      immWrite(0x25,wf&3);
+      chan[7].freqChanged=false;
+    }
+
+    if (chan[7].keyOff || chan[7].keyOn) {
+      writeNoteOn=true;
+      for (int i=0; i<4; i++) {
+        writeMask|=opChan[i].active<<(4+i);
+      }
+    }
+  }
+
   if (writeNoteOn) {
+    if (chan[7].active) { // CSM
+      writeMask^=0xf0;
+    }
     immWrite(0x28,writeMask);
   }
+
+  if (extMode && softPCM) {
+    if (chan[7].keyOn) {
+      immWrite(0x27,0x81);
+      chan[7].keyOn=false;
+    }
+    if (chan[7].keyOff) {
+      immWrite(0x27,0x40);
+      chan[7].keyOff=false;
+    }
+  }
 }
 
 void DivPlatformGenesisExt::forceIns() {