From 06b3950d73016c81e923d3f07263ddf99b8f08bb Mon Sep 17 00:00:00 2001
From: nukeykt <alexeytf2@icloud.com>
Date: Mon, 29 Jan 2018 13:24:13 +0900
Subject: [PATCH] [Core/Sound] accurate YM2612/3438 status read emulation on
 invalid port

---
 core/sound/ym3438.c | 21 ++++++++++++++++++---
 core/sound/ym3438.h |  2 ++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/core/sound/ym3438.c b/core/sound/ym3438.c
index 298bb21..4189c29 100644
--- a/core/sound/ym3438.c
+++ b/core/sound/ym3438.c
@@ -1355,6 +1355,9 @@ void OPN2_Clock(ym3438_t *chip, Bit16s *buffer)
 
     buffer[0] = chip->mol;
     buffer[1] = chip->mor;
+
+    if (chip->status_time)
+        chip->status_time--;
 }
 
 void OPN2_Write(ym3438_t *chip, Bit32u port, Bit8u data)
@@ -1411,18 +1414,30 @@ Bit8u OPN2_Read(ym3438_t *chip, Bit32u port)
             }
             if (chip->mode_test_21[7])
             {
-                return testdata & 0xff;
+                chip->status = testdata & 0xff;
             }
             else
             {
-                return testdata >> 8;
+                chip->status = testdata >> 8;
             }
         }
         else
         {
-            return (chip->busy << 7) | (chip->timer_b_overflow_flag << 1)
+            chip->status = (chip->busy << 7) | (chip->timer_b_overflow_flag << 1)
                  | chip->timer_a_overflow_flag;
         }
+        if (chip_type == ym3438_type_ym2612)
+        {
+            chip->status_time = 300000;
+        }
+        else
+        {
+            chip->status_time = 40000000;
+        }
+    }
+    if (chip->status_time)
+    {
+        return chip->status;
     }
     return 0;
 }
diff --git a/core/sound/ym3438.h b/core/sound/ym3438.h
index baefa0f..c1dc8c5 100644
--- a/core/sound/ym3438.h
+++ b/core/sound/ym3438.h
@@ -205,6 +205,8 @@ typedef struct
     Bit8u pan_l[6], pan_r[6];
     Bit8u ams[6];
     Bit8u pms[6];
+    Bit8u status;
+    Bit32u status_time;
 } ym3438_t;
 
 void OPN2_Reset(ym3438_t *chip);