Merge pull request #18 from izuannazrin/master

Interrupt bit support for ACIA

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

@@ -42,6 +42,7 @@ public abstract class Acia extends Device {
     boolean receiveIrqEnabled = false;
     boolean transmitIrqEnabled = false;
     boolean overrun = false;
+    boolean interrupt = false;
 
     long lastTxWrite   = 0;
     long lastRxRead    = 0;
@@ -100,7 +101,7 @@ public abstract class Acia extends Device {
     /**
      * @return The contents of the status register.
      */
-    public abstract int statusReg();
+    public abstract int statusReg(boolean cpuAccess);
 
     @Override
     public String toString() {
@@ -124,6 +125,7 @@ public abstract class Acia extends Device {
         rxFull = true;
 
         if (receiveIrqEnabled) {
+            interrupt = true;
             getBus().assertIrq();
         }
 
@@ -135,6 +137,7 @@ public abstract class Acia extends Device {
             txEmpty = true;
 
             if (transmitIrqEnabled) {
+                interrupt = true;
                 getBus().assertIrq();
             }
         }

src/main/java/com/loomcom/symon/devices/Acia6551.java

@@ -61,7 +61,7 @@ public class Acia6551 extends Acia {
             case DATA_REG:
                 return rxRead(cpuAccess);
             case STAT_REG:
-                return statusReg();
+                return statusReg(cpuAccess);
             case CMND_REG:
                 return commandRegister;
             case CTRL_REG:
@@ -178,8 +178,8 @@ public class Acia6551 extends Acia {
      * @return The contents of the status register.
      */
     @Override
-    public int statusReg() {
+    public int statusReg(boolean cpuAccess) {
-        // TODO: Parity Error, Framing Error, DTR, DSR, and Interrupt flags.
+        // TODO: Parity Error, Framing Error, DTR, and DSR flags.
         int stat = 0;
         if (rxFull && System.nanoTime() >= (lastRxRead + baudRateDelay)) {
             stat |= 0x08;
@@ -190,6 +190,14 @@ public class Acia6551 extends Acia {
         if (overrun) {
             stat |= 0x04;
         }
+        if (interrupt) {
+            stat |= 0x80;
+        }
+
+        if (cpuAccess) {
+            interrupt = false;
+        }
+
         return stat;
     }
 
@@ -201,6 +209,7 @@ public class Acia6551 extends Acia {
         rxFull = false;
         receiveIrqEnabled = false;
         transmitIrqEnabled = false;
+        interrupt = false;
     }
 
 }

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

@@ -56,9 +56,12 @@ public class Acia6850 extends Acia {
     public int read(int address, boolean cpuAccess) throws MemoryAccessException {
         switch (address) {
             case RX_REG:
+                if (cpuAccess) {
+                    interrupt = false;
+                }
                 return rxRead(cpuAccess);
             case STAT_REG:
-                return statusReg();
+                return statusReg(cpuAccess);
 
             default:
                 throw new MemoryAccessException("No register.");
@@ -69,6 +72,9 @@ public class Acia6850 extends Acia {
     public void write(int address, int data) throws MemoryAccessException {
         switch (address) {
             case TX_REG:
+                if (cpuAccess) {
+                    interrupt = false;
+                }
                 txWrite(data);
                 break;
             case CTRL_REG:
@@ -97,8 +103,8 @@ public class Acia6850 extends Acia {
      * @return The contents of the status register.
      */
     @Override
-    public int statusReg() {
+    public int statusReg(boolean cpuAccess) {
-        // TODO: Parity Error, Framing Error, DTR, DSR, and Interrupt flags.
+        // TODO: Parity Error, Framing Error, DTR, and DSR flags.
         int stat = 0;
         if (rxFull && System.nanoTime() >= (lastRxRead + baudRateDelay)) {
             stat |= 0x01;
@@ -109,6 +115,9 @@ public class Acia6850 extends Acia {
         if (overrun) {
             stat |= 0x20;
         }
+        if (interrupt) {
+            stat |= 0x80;
+        }
 
         return stat;
     }
@@ -118,6 +127,7 @@ public class Acia6850 extends Acia {
         overrun = false;
         rxFull = false;
         txEmpty = true;
+        interrupt = false;
     }
 
 }