M xyw.h → xyw.h

@@ -22,6 +22,7 @@ typedef void (*xyw_writew)(xyw_byte addr, xyw_word val, xyw_byte *error);
 
 typedef struct xyw_device
 {
+    xyw_byte *data;
     xyw_read read;
     xyw_write write;
     xyw_readw readw;

M xywrun.c → xywrun.c

@@ -16,7 +16,8 @@ XYW_ERROR_NONE = 0,
     XYW_ERROR_INVALID_INSTRUCTION,
     XYW_ERROR_STACK_UNDERFLOW,
     XYW_ERROR_STACK_OVERFLOW,
-    XYW_ERROR_DEVICE_UNAVAILABLE
+    XYW_ERROR_DEVICE_UNAVAILABLE,
+    XYW_ERROR_INVALID_DEVICE_PORT
 } xyw_error;
 
 /* system device */
@@ -64,9 +65,16 @@ {
     return (addr - DEVICE_AREA_START) / 16;
 }
 
-static inline xyw_byte get_device_address(xyw_word addr)
+static inline xyw_byte get_device_port(xyw_word addr)
 {
-    return (addr - DEVICE_AREA_START) % 16;
+    // Should return a number between 0 and 15, add validation
+    xyw_byte port = (addr - DEVICE_AREA_START) % 16;
+    if (port >= 16)
+    {
+        *error = XYW_ERROR_INVALID_DEVICE_PORT;
+        return 0xFF;
+    }
+    return port;
 }
 
 //// Read/write memory helpers
@@ -81,7 +89,7 @@ {
             *error = XYW_ERROR_DEVICE_UNAVAILABLE;
             return (xyw_word)-1;
         }
-        xyw_byte dev_addr = get_device_address(addr);
+        xyw_byte dev_addr = get_device_port(addr);
         return xyw_devices[dev_num].readw(dev_addr, error);
     }
     return PEEKW(&xyw_memory[addr]);
@@ -97,7 +105,7 @@ {
             *error = XYW_ERROR_DEVICE_UNAVAILABLE;
             return;
         }
-        xyw_byte dev_addr = get_device_address(addr);
+        xyw_byte dev_addr = get_device_port(addr);
         xyw_devices[dev_num].writew(dev_addr, val, error);
         return;
     }
@@ -114,7 +122,7 @@ {
             *error = XYW_ERROR_DEVICE_UNAVAILABLE;
             return (xyw_byte)-1;
         }
-        xyw_byte dev_addr = get_device_address(addr);
+        xyw_byte dev_addr = get_device_port(addr);
         return xyw_devices[dev_num].read(dev_addr, error);
     }
     return xyw_memory[addr];
@@ -130,7 +138,7 @@ {
             *error = XYW_ERROR_DEVICE_UNAVAILABLE;
             return;
         }
-        xyw_byte dev_addr = get_device_address(addr);
+        xyw_byte dev_addr = get_device_port(addr);
         xyw_devices[dev_num].write(dev_addr, val, error);
         return;
     }