Issue #16: Memory window should not reset device registers

src/main/java/com/loomcom/symon/devices/Acia6850.java

@@ -53,10 +53,10 @@ public class Acia6850 extends Acia {
     }
 
     @Override
-    public int read(int address) throws MemoryAccessException {
+    public int read(int address, boolean cpuAccess) throws MemoryAccessException {
         switch (address) {
             case RX_REG:
-                return rxRead();
+                return rxRead(cpuAccess);
             case STAT_REG:
                 return statusReg();