From 49317e9165263ba01df5d875f07081786a51241e Mon Sep 17 00:00:00 2001
From: Arisotura <thetotalworm@gmail.com>
Date: Fri, 11 Dec 2020 18:06:26 +0100
Subject: don't axe error bits when writing to IPCFIFOCNT. fixes #801

---
 src/NDS.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/NDS.cpp b/src/NDS.cpp
index b8b83f7..8b49328 100644
--- a/src/NDS.cpp
+++ b/src/NDS.cpp
@@ -3245,7 +3245,7 @@ void ARM9IOWrite16(u32 addr, u16 val)
             SetIRQ(0, IRQ_IPCRecv);
         if (val & 0x4000)
             IPCFIFOCnt9 &= ~0x4000;
-        IPCFIFOCnt9 = val & 0x8404;
+        IPCFIFOCnt9 = (val & 0x8404) | (IPCFIFOCnt9 & 0x4000);
         return;
 
     case 0x04000188:
@@ -3848,7 +3848,7 @@ void ARM7IOWrite16(u32 addr, u16 val)
             SetIRQ(1, IRQ_IPCRecv);
         if (val & 0x4000)
             IPCFIFOCnt7 &= ~0x4000;
-        IPCFIFOCnt7 = val & 0x8404;
+        IPCFIFOCnt7 = (val & 0x8404) | (IPCFIFOCnt7 & 0x4000);
         return;
 
     case 0x04000188:
-- 
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