[Mega-CD] fix wordram dual bank access

jotego · Mar 22, 2021 · 52af4eb · 52af4eb
1 parent 205c90d
commit 52af4eb
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Showing 3 changed files with 43 additions and 12 deletions.
diff --git a/higan/md/mcd/bus-external.cpp b/higan/md/mcd/bus-external.cpp
@@ -15,7 +15,11 @@ auto MCD::external_read(uint1 upper, uint1 lower, uint22 address, uint16 data) -
     //if(io.wramSwitch == 1) return data;
       address = (uint18)address;
     } else {
-      address = (uint17)address << 1 | io.wramSelect == 0;
+      // TODO: bitmapped mode when reading $220000 thru $23ffff in 1M mode
+      if(io.wramSelect == 0)
+        address = (uint17)address + 0x020000;
+      else
+        address = (uint17)address;
     }
     if(!vdp.active()) return wram[address >> 1];
 
@@ -45,7 +49,11 @@ auto MCD::external_write(uint1 upper, uint1 lower, uint22 address, uint16 data)
     //if(io.wramSwitch == 1) return;
       address = (uint18)address;
     } else {
-      address = (uint17)address << 1 | io.wramSelect == 0;
+      // TODO: bitmapped mode when writing $220000 thru $23ffff in 1M mode
+      if(io.wramSelect == 0)
+        address = (uint17)address + 0x020000;
+      else
+        address = (uint17)address;
     }
     if(upper) wram[address >> 1].byte(1) = data.byte(1);
     if(lower) wram[address >> 1].byte(0) = data.byte(0);

diff --git a/higan/md/mcd/bus.cpp b/higan/md/mcd/bus.cpp
@@ -5,14 +5,24 @@ auto MCD::read(uint1 upper, uint1 lower, uint24 address, uint16 data) -> uint16
     return pram[address >> 1];
   }
 
-  if(address >= 0x080000 && address <= 0x0dffff) {
+  if(address >= 0x080000 && address <= 0x0bffff) {
     if(io.wramMode == 0) {
     //if(io.wramSwitch == 0) return data;
       address = (uint18)address;
-    } else {
-      address = (uint17)address << 1 | io.wramSelect == 1;
+      return wram[address >> 1];
     }
-    return wram[address >> 1];
+    return data;
+  }
+
+  if(address >= 0x0c0000 && address <= 0x0dffff) {
+    if(io.wramMode == 1) {
+      if(io.wramSelect == 0)
+        address = (uint17)address;
+      else
+        address = (uint17)address + 0x020000;
+      return wram[address >> 1];
+    }
+    return data;
   }
 
   if(address >= 0x0e0000 && address <= 0x0effff) {
@@ -41,15 +51,25 @@ auto MCD::write(uint1 upper, uint1 lower, uint24 address, uint16 data) -> void {
     return;
   }
 
-  if(address >= 0x080000 && address <= 0x0dffff) {
+  if(address >= 0x080000 && address <= 0x0bffff) {
     if(io.wramMode == 0) {
     //if(io.wramSwitch == 0) return;
       address = (uint18)address;
-    } else {
-      address = (uint17)address << 1 | io.wramSelect == 1;
+      if(upper) wram[address >> 1].byte(1) = data.byte(1);
+      if(lower) wram[address >> 1].byte(0) = data.byte(0);
+    }
+    return;
+  }
+
+  if(address >= 0x0c0000 && address <= 0x0dffff) {
+    if(io.wramMode == 1) {
+      if(io.wramSelect == 0)
+        address = (uint17)address;
+      else
+        address = (uint17)address + 0x020000;
+      if(upper) wram[address >> 1].byte(1) = data.byte(1);
+      if(lower) wram[address >> 1].byte(0) = data.byte(0);
     }
-    if(upper) wram[address >> 1].byte(1) = data.byte(1);
-    if(lower) wram[address >> 1].byte(0) = data.byte(0);
     return;
   }
 

diff --git a/higan/md/mcd/cdc-transfer.cpp b/higan/md/mcd/cdc-transfer.cpp
@@ -15,7 +15,10 @@ auto MCD::CDC::Transfer::dma() -> void {
     break;
 
   case 7:  //WRAM
-    mcd.write(1, 1, 0x080000 | (uint18)address & ~1, data);
+    if(mcd.io.wramMode == 0)
+      mcd.write(1, 1, 0x080000 | (uint18)address & ~1, data);
+    else
+      mcd.write(1, 1, 0x0C0000 | (uint17)address & ~1, data);
     break;
   }