From 87b172015ce02efa1a8d5a503ccb6a4e4c54caed Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Wed, 28 Aug 2024 17:07:05 -0500
Subject: [PATCH] fix 601x-604x

---
 src/engine/platform/arcade.cpp  | 15 ++++++++++++++-
 src/engine/platform/genesis.cpp | 15 ++++++++++++++-
 src/engine/platform/ym2203.cpp  | 15 ++++++++++++++-
 src/engine/platform/ym2608.cpp  | 15 ++++++++++++++-
 src/engine/platform/ym2610.cpp  | 15 ++++++++++++++-
 src/engine/platform/ym2610b.cpp | 15 ++++++++++++++-
 6 files changed, 84 insertions(+), 6 deletions(-)

diff --git a/src/engine/platform/arcade.cpp b/src/engine/platform/arcade.cpp
index 74cfcc6e7..d46976bb0 100644
--- a/src/engine/platform/arcade.cpp
+++ b/src/engine/platform/arcade.cpp
@@ -762,7 +762,20 @@ int DivPlatformArcade::dispatch(DivCommand c) {
       break;
     }
     case DIV_CMD_FM_OPMASK:
-      chan[c.chan].opMask=c.value&15;
+      switch (c.value>>4) {
+        case 1:
+        case 2:
+        case 3:
+        case 4:
+          chan[c.chan].opMask&=~(1<<((c.value>>4)-1));
+          if (c.value&15) {
+            chan[c.chan].opMask|=(1<<((c.value>>4)-1));
+          }
+          break;
+        default:
+          chan[c.chan].opMask=c.value&15;
+          break;
+      }
       if (chan[c.chan].active) {
         chan[c.chan].opMaskChanged=true;
       }
diff --git a/src/engine/platform/genesis.cpp b/src/engine/platform/genesis.cpp
index 1b8707896..4bf56581e 100644
--- a/src/engine/platform/genesis.cpp
+++ b/src/engine/platform/genesis.cpp
@@ -1465,7 +1465,20 @@ int DivPlatformGenesis::dispatch(DivCommand c) {
     }
     case DIV_CMD_FM_OPMASK:
       if (c.chan>=psgChanOffs) break;
-      chan[c.chan].opMask=c.value&15;
+      switch (c.value>>4) {
+        case 1:
+        case 2:
+        case 3:
+        case 4:
+          chan[c.chan].opMask&=~(1<<((c.value>>4)-1));
+          if (c.value&15) {
+            chan[c.chan].opMask|=(1<<((c.value>>4)-1));
+          }
+          break;
+        default:
+          chan[c.chan].opMask=c.value&15;
+          break;
+      }
       if (chan[c.chan].active) {
         chan[c.chan].opMaskChanged=true;
       }
diff --git a/src/engine/platform/ym2203.cpp b/src/engine/platform/ym2203.cpp
index 2a19fea0f..c1774f4fc 100644
--- a/src/engine/platform/ym2203.cpp
+++ b/src/engine/platform/ym2203.cpp
@@ -1006,7 +1006,20 @@ int DivPlatformYM2203::dispatch(DivCommand c) {
     }
     case DIV_CMD_FM_OPMASK:
       if (c.chan>=psgChanOffs) break;
-      chan[c.chan].opMask=c.value&15;
+      switch (c.value>>4) {
+        case 1:
+        case 2:
+        case 3:
+        case 4:
+          chan[c.chan].opMask&=~(1<<((c.value>>4)-1));
+          if (c.value&15) {
+            chan[c.chan].opMask|=(1<<((c.value>>4)-1));
+          }
+          break;
+        default:
+          chan[c.chan].opMask=c.value&15;
+          break;
+      }
       if (chan[c.chan].active) {
         chan[c.chan].opMaskChanged=true;
       }
diff --git a/src/engine/platform/ym2608.cpp b/src/engine/platform/ym2608.cpp
index 046e20c20..825c3b5ac 100644
--- a/src/engine/platform/ym2608.cpp
+++ b/src/engine/platform/ym2608.cpp
@@ -1539,7 +1539,20 @@ int DivPlatformYM2608::dispatch(DivCommand c) {
     }
     case DIV_CMD_FM_OPMASK:
       if (c.chan>=psgChanOffs) break;
-      chan[c.chan].opMask=c.value&15;
+      switch (c.value>>4) {
+        case 1:
+        case 2:
+        case 3:
+        case 4:
+          chan[c.chan].opMask&=~(1<<((c.value>>4)-1));
+          if (c.value&15) {
+            chan[c.chan].opMask|=(1<<((c.value>>4)-1));
+          }
+          break;
+        default:
+          chan[c.chan].opMask=c.value&15;
+          break;
+      }
       if (chan[c.chan].active) {
         chan[c.chan].opMaskChanged=true;
       }
diff --git a/src/engine/platform/ym2610.cpp b/src/engine/platform/ym2610.cpp
index 038cbc807..d64b49569 100644
--- a/src/engine/platform/ym2610.cpp
+++ b/src/engine/platform/ym2610.cpp
@@ -1509,7 +1509,20 @@ int DivPlatformYM2610::dispatch(DivCommand c) {
     }
     case DIV_CMD_FM_OPMASK:
       if (c.chan>=psgChanOffs) break;
-      chan[c.chan].opMask=c.value&15;
+      switch (c.value>>4) {
+        case 1:
+        case 2:
+        case 3:
+        case 4:
+          chan[c.chan].opMask&=~(1<<((c.value>>4)-1));
+          if (c.value&15) {
+            chan[c.chan].opMask|=(1<<((c.value>>4)-1));
+          }
+          break;
+        default:
+          chan[c.chan].opMask=c.value&15;
+          break;
+      }
       if (chan[c.chan].active) {
         chan[c.chan].opMaskChanged=true;
       }
diff --git a/src/engine/platform/ym2610b.cpp b/src/engine/platform/ym2610b.cpp
index 8b12ca862..b5f555f58 100644
--- a/src/engine/platform/ym2610b.cpp
+++ b/src/engine/platform/ym2610b.cpp
@@ -1578,7 +1578,20 @@ int DivPlatformYM2610B::dispatch(DivCommand c) {
     }
     case DIV_CMD_FM_OPMASK:
       if (c.chan>=psgChanOffs) break;
-      chan[c.chan].opMask=c.value&15;
+      switch (c.value>>4) {
+        case 1:
+        case 2:
+        case 3:
+        case 4:
+          chan[c.chan].opMask&=~(1<<((c.value>>4)-1));
+          if (c.value&15) {
+            chan[c.chan].opMask|=(1<<((c.value>>4)-1));
+          }
+          break;
+        default:
+          chan[c.chan].opMask=c.value&15;
+          break;
+      }
       if (chan[c.chan].active) {
         chan[c.chan].opMaskChanged=true;
       }