Merge pull request #213 from rjpontefract/rp/68000_memory

CiscOS memory map changes
stardot · Oct 21, 2023 · ac1baae · ac1baae
2 parents 2c3bdbd + 4dbf13d
commit ac1baae
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Showing 3 changed files with 36 additions and 32 deletions.
diff --git a/src/mc68000tube.c b/src/mc68000tube.c
@@ -1,3 +1,4 @@
+
 #include "b-em.h"
 #include "cpu_debug.h"
 #include "tube.h"
@@ -21,23 +22,22 @@ static uint8_t readmem(uint32_t addr)
             return data;
         }
     }
-    if (addr < MC68000_RAM_SIZE) {
-        uint8_t data = mc68000_ram[addr];
-        //log_debug("mc68000: read %08X as RAM -> %02X", addr, data);
+    uint32_t top = addr & 0xFFFF0000;
+    if (top == 0xFFFF0000) {
+        uint8_t data = mc68000_rom[addr & 0x7FFF];
+        //log_debug("mc68000: read %08X as high ROM -> %02X", addr, data);
         return data;
     }
-    else {
-        uint32_t top = addr & 0xFFFF0000;
-        if (top == 0xFFFF0000) {
-            uint8_t data = mc68000_rom[addr & 0x7FFF];
-            //log_debug("mc68000: read %08X as high ROM -> %02X", addr, data);
-            return data;
-        }
-        else if (top == 0xFFFE0000) {
-            uint8_t data = tube_parasite_read(addr);
-            //log_debug("mc68000: read %08X as I/O -> %02X (%d cycles left)", addr, data, m68k_cycles_remaining());
-            return data;
-        }
+    else if (top == 0xFFFE0000) {
+        uint8_t data = tube_parasite_read(addr);
+        //log_debug("mc68000: read %08X as I/O -> %02X (%d cycles left)", addr, data, m68k_cycles_remaining());
+        return data;
+    }
+    else
+    {
+        uint8_t data = mc68000_ram[addr % MC68000_RAM_SIZE];
+        log_debug("mc68000: read %08X as RAM -> %02X", addr, data);
+        return data;
     }
     log_debug("mc68000: read %08X unmapped", addr);
     return 0xff;
@@ -84,21 +84,20 @@ unsigned int m68k_read_disassembler_32 (unsigned int address)
 
 static void writemem(uint32_t addr, uint8_t data)
 {
-    if (addr < MC68000_RAM_SIZE) {
-        //log_debug("mc68000: write %08X as RAM <- %02X", addr, data);
-        mc68000_ram[addr] = data;
-    }
-    else {
-        uint32_t top = addr & 0xFFFF0000;
-        if (top == 0xfffe0000) {
-            //log_debug("mc68000: write %09X as I/O <- %02X", addr, data);
-            tube_parasite_write(addr, data);
-        }
-        else if (top == 0xffff0000)
-            log_debug("mc68000: write %08X as ROM (ignored) <- %02X", addr, data);
-        else
-            log_debug("mc68000: write %08X as unmapped (ignored) <- %02X", addr, data);
-    }
+  uint32_t top = addr & 0xFFFF0000;
+  if (top == 0xFFFE0000) {
+      //log_debug("mc68000: write %09X as I/O <- %02X", addr, data);
+      tube_parasite_write(addr, data);
+  }
+  else if (top == 0xFFFF0000)
+  {
+      log_debug("mc68000: write %08X as ROM (ignored) <- %02X", addr, data);
+  }
+  else
+  {
+    log_debug("mc68000: write %08X as RAM <- %02X", addr, data);
+    mc68000_ram[addr % MC68000_RAM_SIZE] = data;
+  }
 }
 
 void m68k_write_memory_8(unsigned int address, unsigned int value)

diff --git a/src/mc68000tube.h b/src/mc68000tube.h
@@ -3,7 +3,7 @@
 
 #include <stdbool.h>
 
-#define MC68000_RAM_SIZE 0x3F0000
+#define MC68000_RAM_SIZE 0x800000
 #define MC68000_ROM_SIZE 0x8000
 
 extern bool tube_68000_init(void *rom);

diff --git a/src/model.h b/src/model.h
@@ -55,7 +55,12 @@ typedef struct
     int  speed_multiplier;
 } TUBE;
 
-#define NUM_TUBES 13
+#ifdef M68K
+# define NUM_TUBES 14
+#else
+# define NUM_TUBES 13
+#endif
+
 extern TUBE tubes[NUM_TUBES];
 
 extern int curmodel, curtube, oldmodel, selecttube;