diff --git a/HISTORY.txt b/HISTORY.txt
index 99e32c0..8de9980 100644
--- a/HISTORY.txt
+++ b/HISTORY.txt
@@ -33,7 +33,8 @@ Genesis Plus GX 1.7.5 (xx/xx/xxxx) (Eke-Eke)
 * fixed incorrect masking of Level 3 (GFX) interrupts (spurious freeze during Japanese BIOS intro)
 * fixed H-INT vector handling when using Mode 1
 * fixed access to "write-only" communication flags (verified on real hardware by Notaz)
-* fixed pending level 1 interrupts when GFX interrupt is disabled (fixes random freezes out of "Batman Returns" option menu)
+* fixed access to Sub-CPU "read-only" communication registers (fixes Round 5 Boss freeze in Streets of Rage / Sega Classics Arcade Collection)
+* fixed pending level 1 interrupts when GFX interrupt is disabled (fixes random freezes when exiting "Batman Returns" option menu)
 * fixed CDD seek command again (Final Fight CD freeze with model 2 BIOS)
 * optimized Sub-CPU / Main-CPU synchronization
 
diff --git a/builds/genesis_plus_gx_libretro.dll b/builds/genesis_plus_gx_libretro.dll
index a740e46..d2c8295 100644
Binary files a/builds/genesis_plus_gx_libretro.dll and b/builds/genesis_plus_gx_libretro.dll differ
diff --git a/builds/genplus_cube.dol b/builds/genplus_cube.dol
index 065cb9b..ec11ffa 100644
Binary files a/builds/genplus_cube.dol and b/builds/genplus_cube.dol differ
diff --git a/builds/genplus_wii.dol b/builds/genplus_wii.dol
index 448d26d..5902708 100644
Binary files a/builds/genplus_wii.dol and b/builds/genplus_wii.dol differ
diff --git a/core/cd_hw/scd.c b/core/cd_hw/scd.c
index f3fa2be..fdf49d0 100644
--- a/core/cd_hw/scd.c
+++ b/core/cd_hw/scd.c
@@ -1010,11 +1010,18 @@ static void scd_write_byte(unsigned int address, unsigned int data)
     default:
     {
       /* SUB-CPU communication words */
-      if ((address & 0xf0) == 0x20)
+      if ((address & 0x1f0) == 0x20)
       {
         s68k_poll_sync(1 << ((address - 0x10) & 0x1f));
       }
 
+      /* MAIN-CPU communication words */
+      else if ((address & 0x1f0) == 0x10)
+      {
+        /* read-only (Sega Classic Arcade Collection) */
+        return;
+      }
+
       /* default registers */
       if (address & 1)
       {
@@ -1297,11 +1304,18 @@ static void scd_write_word(unsigned int address, unsigned int data)
     default:
     {
       /* SUB-CPU communication words */
-      if ((address & 0xf0) == 0x20)
+      if ((address & 0x1f0) == 0x20)
       {
         s68k_poll_sync(3 << ((address - 0x10) & 0x1e));
       }
 
+      /* MAIN-CPU communication words */
+      else if ((address & 0x1f0) == 0x10)
+      {
+        /* read-only (Sega Classic Arcade Collection) */
+        return;
+      }
+
       /* default registers */
       scd.regs[(address >> 1) & 0xff].w = data;
       return;