From 1b18426c5cd5634a71c0ca96142107660c9e28ce Mon Sep 17 00:00:00 2001
From: Brent O'Neil <mebeme98@gmail.com>
Date: Sat, 30 Dec 2017 02:02:18 +1100
Subject: [PATCH] Added the Interupt (int <imm>) and Return from Interupt
 (intr) command.

Interupt pushes the flag register and the instruction pointer, then resets
execution to 0x0200 + (imm)*2.

Return from interupt pops the flags back and sets the ip. Returning execution
to the interupting code.

Implemented using a CPU hook that can be used to later implement interupts generated
from hardware, or for errors like divide by 0.
---
 .../net/simon987/server/assembly/CPU.java     | 14 ++++++--
 .../net/simon987/server/assembly/Status.java  | 16 +++++++++
 .../assembly/instruction/IntInstruction.java  | 35 +++++++++++++++++++
 .../assembly/instruction/IntrInstruction.java | 26 ++++++++++++++
 4 files changed, 89 insertions(+), 2 deletions(-)
 create mode 100644 Server/src/main/java/net/simon987/server/assembly/instruction/IntInstruction.java
 create mode 100644 Server/src/main/java/net/simon987/server/assembly/instruction/IntrInstruction.java

diff --git a/Server/src/main/java/net/simon987/server/assembly/CPU.java b/Server/src/main/java/net/simon987/server/assembly/CPU.java
index 0a8efe9..f8cfc3e 100755
--- a/Server/src/main/java/net/simon987/server/assembly/CPU.java
+++ b/Server/src/main/java/net/simon987/server/assembly/CPU.java
@@ -97,6 +97,8 @@ public class CPU implements JSONSerialisable {
         instructionSet.add(new JncInstruction(this));
         instructionSet.add(new JnoInstruction(this));
         instructionSet.add(new JoInstruction(this));
+        instructionSet.add(new IntInstruction(this));
+        instructionSet.add(new IntrInstruction(this));
 
         status = new Status();
         memory = new Memory(config.getInt("memory_size"));
@@ -466,6 +468,14 @@ public class CPU implements JSONSerialisable {
         return attachedHardware.get(address);
 
     }
-
-
+    /**
+     * Sets the IP to 0x0200 + Offset and pushes flags then the old IP
+     * 
+     */
+    public void Interrupt(int hw, int offset, boolean retry) {
+    	Instruction push = instructionSet.get("push");
+    	push.execute(status.toByte(), status);
+        push.execute(ip, status);
+		this.setIp((char)(0x0200 + offset*2 + 0x0080*hw));
+    }    
 }
diff --git a/Server/src/main/java/net/simon987/server/assembly/Status.java b/Server/src/main/java/net/simon987/server/assembly/Status.java
index 4b370a6..2bea560 100755
--- a/Server/src/main/java/net/simon987/server/assembly/Status.java
+++ b/Server/src/main/java/net/simon987/server/assembly/Status.java
@@ -132,4 +132,20 @@ public class Status {
     public void setErrorFlag(boolean errorFlag) {
         this.errorFlag = errorFlag;
     }
+    
+    public char toByte() {
+    	char stat = 0; 
+    	stat = (char) (stat | ((signFlag ? 1 : 0) << 3));
+    	stat = (char) (stat | ((zeroFlag ? 1 : 0) << 2));
+    	stat = (char) (stat | ((carryFlag ? 1 : 0) << 1));
+    	stat = (char) (stat | (overflowFlag ? 1 : 0));
+    	return stat;
+    }
+    
+    public void fromByte(char stat) {
+    	setSignFlag((stat & (1 << 3)) != 0);
+    	setZeroFlag((stat & (1 << 2)) != 0);
+    	setCarryFlag((stat & (1 << 1)) != 0);
+    	setOverflowFlag((stat & 1) != 0);    	
+    }
 }
diff --git a/Server/src/main/java/net/simon987/server/assembly/instruction/IntInstruction.java b/Server/src/main/java/net/simon987/server/assembly/instruction/IntInstruction.java
new file mode 100644
index 0000000..3a90690
--- /dev/null
+++ b/Server/src/main/java/net/simon987/server/assembly/instruction/IntInstruction.java
@@ -0,0 +1,35 @@
+package net.simon987.server.assembly.instruction;
+
+import net.simon987.server.assembly.CPU;
+import net.simon987.server.assembly.Instruction;
+import net.simon987.server.assembly.Status;
+/**
+ *  Sets the PC to 0x0200 + Immediate operand
+ *  
+ * 
+ *
+ */
+public class IntInstruction extends Instruction{
+	
+	public static final int OPCODE = 48;
+	private CPU cpu;
+
+	public IntInstruction(CPU cpu) {
+		super("int", OPCODE);
+		this.cpu = cpu;
+	}
+	
+	@Override	
+    public Status execute(int src, Status status) {
+		cpu.Interrupt(0, src, false);
+        return status;
+    }
+
+	
+    public Status execute(Status status) {
+    	cpu.Interrupt(0,0, false);
+        return status;
+    }
+	
+
+}
diff --git a/Server/src/main/java/net/simon987/server/assembly/instruction/IntrInstruction.java b/Server/src/main/java/net/simon987/server/assembly/instruction/IntrInstruction.java
new file mode 100644
index 0000000..feaf846
--- /dev/null
+++ b/Server/src/main/java/net/simon987/server/assembly/instruction/IntrInstruction.java
@@ -0,0 +1,26 @@
+package net.simon987.server.assembly.instruction;
+
+import net.simon987.server.assembly.CPU;
+import net.simon987.server.assembly.Instruction;
+import net.simon987.server.assembly.Status;
+
+public class IntrInstruction extends Instruction{
+			
+		public static final int OPCODE = 49;
+		private CPU cpu;
+
+		public IntrInstruction(CPU cpu) {
+			super("intr", OPCODE);
+			this.cpu = cpu;
+		}
+		
+	    public Status execute(Status status) {
+	    	cpu.setIp((char)cpu.getMemory().get(cpu.getRegisterSet().getRegister("SP").getValue()));
+	        status.fromByte((char) cpu.getMemory().get(cpu.getRegisterSet().getRegister("SP").getValue() + 1));	        
+	        cpu.getRegisterSet().getRegister("SP").setValue(cpu.getRegisterSet().getRegister("SP").getValue() + 2); //Increment SP (stack grows towards smaller)
+	        return status;
+	    }
+		
+
+}
+