From 88a14fb5f2d85e8477957f8ac4ead84ded719b50 Mon Sep 17 00:00:00 2001
From: Luke Usher <luke@usher.cc>
Date: Wed, 18 Oct 2023 20:00:23 +0100
Subject: [PATCH] msx: fix conflicts between rom and scc with KonamiSCC mapper

---
 ares/msx/cartridge/board/konami-scc.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/ares/msx/cartridge/board/konami-scc.cpp b/ares/msx/cartridge/board/konami-scc.cpp
index 44e6aabe84..ca51ba81b9 100644
--- a/ares/msx/cartridge/board/konami-scc.cpp
+++ b/ares/msx/cartridge/board/konami-scc.cpp
@@ -48,6 +48,9 @@ struct KonamiSCC : Interface {
     if(address >= 0x0000 && address <= 0x1fff) data = rom.read(bank[2] << 13 | (n13)address);
     if(address >= 0x2000 && address <= 0x3fff) data = rom.read(bank[3] << 13 | (n13)address);
 
+    //scc is mapped in bank 0x3f for 98xx-98ff
+    if(bank[2].bit(0, 5) != 0x3f) return data;
+
     address.bit(8) = 0;  //SCC ignores A8
 
     if(address >= 0x9800 && address <= 0x981f) {
@@ -88,6 +91,9 @@ struct KonamiSCC : Interface {
     if(address >= 0x9000 && address <= 0x97ff) bank[2] = data;
     if(address >= 0xb000 && address <= 0xb7ff) bank[3] = data;
 
+    //scc is mapped in bank 0x3f for 98xx-98ff
+    if(bank[2].bit(0, 5) != 0x3f) return;
+
     address.bit(8) = 0;  //SCC ignores A8
 
     if(address >= 0x9800 && address <= 0x981f && !test.bit(6)) {