From b6cc4809192d2eed4d4162e51f845d19ef9d2445 Mon Sep 17 00:00:00 2001
From: Seth Morabito <web@loomcom.com>
Date: Sat, 25 Jan 2014 20:02:17 -0800
Subject: [PATCH] Add NMI flag to CPU

---
 src/main/java/com/loomcom/symon/Bus.java     | 20 +++++++++---
 src/main/java/com/loomcom/symon/Cpu.java     | 34 ++++++++++++++------
 src/test/java/com/loomcom/symon/BusTest.java | 28 ++++++++++++----
 3 files changed, 62 insertions(+), 20 deletions(-)

diff --git a/src/main/java/com/loomcom/symon/Bus.java b/src/main/java/com/loomcom/symon/Bus.java
index 429853b..650df3c 100644
--- a/src/main/java/com/loomcom/symon/Bus.java
+++ b/src/main/java/com/loomcom/symon/Bus.java
@@ -151,15 +151,27 @@ public class Bus {
         throw new MemoryAccessException("Bus write failed. No device at address " + String.format("$%04X", address));
     }
 
-    public void assertInterrupt() {
+    public void assertIrq() {
         if (cpu != null) {
-            cpu.assertInterrupt();
+            cpu.assertIrq();
         }
     }
 
-    public void clearInterrupt() {
+    public void clearIrq() {
         if (cpu != null) {
-            cpu.clearInterrupt();
+            cpu.clearIrq();
+        }
+    }
+
+    public void assertNmi() {
+        if (cpu != null) {
+            cpu.assertNmi();
+        }
+    }
+
+    public void clearNmi() {
+        if (cpu != null) {
+            cpu.clearNmi();
         }
     }
 
diff --git a/src/main/java/com/loomcom/symon/Cpu.java b/src/main/java/com/loomcom/symon/Cpu.java
index c5ab304..85a6cba 100644
--- a/src/main/java/com/loomcom/symon/Cpu.java
+++ b/src/main/java/com/loomcom/symon/Cpu.java
@@ -133,7 +133,7 @@ public class Cpu implements InstructionTable {
         state.overflowFlag = false;
         state.negativeFlag = false;
 
-        state.interruptAsserted = false;
+        state.irqAsserted = false;
 
         // Clear illegal opcode trap.
         state.opTrap = false;
@@ -154,7 +154,7 @@ public class Cpu implements InstructionTable {
     }
 
     /**
-     * Performs an individual machine cycle.
+     * Performs an individual instruction cycle.
      */
     public void step() throws MemoryAccessException {
         // Store the address from which the IR was read, for debugging
@@ -1168,15 +1168,29 @@ public class Cpu implements InstructionTable {
     /**
      * Simulate transition from logic-high to logic-low on the INT line.
      */
-    public void assertInterrupt() {
-       state.interruptAsserted = true;
+    public void assertIrq() {
+       state.irqAsserted = true;
     }
 
     /**
      * Simulate transition from logic-low to logic-high of the INT line.
      */
-    public void clearInterrupt() {
-        state.interruptAsserted = false;
+    public void clearIrq() {
+        state.irqAsserted = false;
+    }
+
+    /**
+     * Simulate transition from logic-high to logic-low on the NMI line.
+     */
+    public void assertNmi() {
+        state.nmiAsserted = true;
+    }
+
+    /**
+     * Simulate transition from logic-low to logic-high of the NMI line.
+     */
+    public void clearNmi() {
+        state.nmiAsserted = false;
     }
 
     /**
@@ -1323,8 +1337,8 @@ public class Cpu implements InstructionTable {
         public int[] args = new int[2];
         public int instSize;
         public boolean opTrap;
-        /* True if the INT line was held low */
-        public boolean interruptAsserted;
+        public boolean irqAsserted;
+        public boolean nmiAsserted;
 
         /* Status Flag Register bits */
         public boolean carryFlag;
@@ -1361,7 +1375,7 @@ public class Cpu implements InstructionTable {
             this.args[1] = s.args[1];
             this.instSize = s.instSize;
             this.opTrap = s.opTrap;
-            this.interruptAsserted = s.interruptAsserted;
+            this.irqAsserted = s.irqAsserted;
             this.carryFlag = s.carryFlag;
             this.negativeFlag = s.negativeFlag;
             this.zeroFlag = s.zeroFlag;
@@ -1370,7 +1384,7 @@ public class Cpu implements InstructionTable {
             this.breakFlag = s.breakFlag;
             this.overflowFlag = s.overflowFlag;
             this.stepCounter = s.stepCounter;
-                    }
+        }
 
         /**
          * Returns a string formatted for the trace log.
diff --git a/src/test/java/com/loomcom/symon/BusTest.java b/src/test/java/com/loomcom/symon/BusTest.java
index f2eb35a..b4a8a9a 100644
--- a/src/test/java/com/loomcom/symon/BusTest.java
+++ b/src/test/java/com/loomcom/symon/BusTest.java
@@ -119,20 +119,36 @@ public class BusTest extends TestCase {
         assertTrue("Address space should have been complete!", b.isComplete());
     }
 
-    public void testSetAndClearInterrupt() throws Exception {
+    public void testSetAndClearIrq() throws Exception {
         Bus b = new Bus(0x0000, 0xffff);
         Cpu c = new Cpu();
         b.addCpu(c);
 
-        assertFalse(c.getCpuState().interruptAsserted);
+        assertFalse(c.getCpuState().irqAsserted);
 
-        b.assertInterrupt();
+        b.assertIrq();
 
-        assertTrue(c.getCpuState().interruptAsserted);
+        assertTrue(c.getCpuState().irqAsserted);
 
-        b.clearInterrupt();
+        b.clearIrq();
 
-        assertFalse(c.getCpuState().interruptAsserted);
+        assertFalse(c.getCpuState().irqAsserted);
+    }
+
+    public void testSetAndClearNmi() throws Exception {
+        Bus b = new Bus(0x0000, 0xffff);
+        Cpu c = new Cpu();
+        b.addCpu(c);
+
+        assertFalse(c.getCpuState().nmiAsserted);
+
+        b.assertNmi();
+
+        assertTrue(c.getCpuState().nmiAsserted);
+
+        b.clearNmi();
+
+        assertFalse(c.getCpuState().nmiAsserted);
     }
 
 }