Fixed issues with CALL/RET.

Added Test Program for CALL/RET.
Fixed MUL instruction.

SVM/Instructions/CALL.cs

@@ -44,7 +44,8 @@ namespace SVM.Instructions
             Debug.Assert(vm.SP < VM.STACKDEPTH);
 
             vm.STACK[vm.SP++] = vm.PC;
-            vm.PC = (ushort)((vars[0] << 8) + vars[1]);
+            var jmp = (ushort)((vars[0] << 8) + vars[1]);
+            vm.PC = jmp;
         }
 
         public override string ToASM(byte[] vars)

SVM/Instructions/MUL.cs

@@ -6,7 +6,7 @@ namespace SVM.Instructions
 {
     class MUL : ADD
     {
-        public override string ASM => "SUB";
+        public override string ASM => "MUL";
 
         public override byte OP => 0x24;
         

SVM/Instructions/RET.cs

@@ -19,10 +19,11 @@ namespace SVM.Instructions
         public override void Exec(VM vm, byte[] vars)
         {
             Debug.Assert(vars.Length == 0);
-            Debug.Assert(vm.SP >= 0);
+            Debug.Assert(vm.SP > 0);
 
+            vm.SP--;
             vm.PC = vm.STACK[vm.SP];
-            vm.STACK[vm.SP--] = 0;
+            vm.STACK[vm.SP] = 0;
         }
 
         public override string ToASM(byte[] vars)

SVM/PGM/CALL.txt

@@ -0,0 +1,29 @@
+ORIGIN 0
+JMP :PGM
+
+:WRITESTR
+SETI A
+:WRITESTR_LOOP
+LOADI A
+JZ A :WRITESTR_RET
+SAVE A P 0
+INCI
+JMP :WRITESTR_LOOP
+:WRITESTR_RET
+RET
+
+:WRITENL
+LOAD A L 13
+SAVE A P 0
+LOAD A L 10
+SAVE A P 0
+RET
+
+:PGM
+LOAD A L 0x100
+CALL :WRITESTR
+CALL :WRITENL
+HALT
+
+MEMORY
+0x100	"CALL/RET Test"

SVM/Program.cs

@@ -7,8 +7,18 @@ namespace SVM
     {
         static void Main(string[] args)
         {
+            if (args.Length == 0)
+            {
+                Console.WriteLine("Usage: dotnet SVN.dll [Filename]");
+                return;
+            }
             var file = Path.Combine(Environment.CurrentDirectory, args[0]);
 
+            if (!File.Exists(file))
+            {
+                Console.WriteLine("Error: File Not Found");
+            }
+
             var content = File.ReadAllText(file);
 
             Console.WriteLine("Assembling {0}", file);
@@ -16,7 +26,8 @@ namespace SVM
             var asm = new Assembler();
 
             var mem = asm.Compile(content);
-
+            Console.WriteLine("Compiled to {0} bytes", mem.Length);
+            
             var vm = new VM();
             vm.CycleDelay = 25;
             vm.Load(mem, 0);

SVM/SVM.csproj

@@ -3,14 +3,20 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp2.0</TargetFramework>
+    <StartupObject></StartupObject>
+    <ApplicationIcon />
   </PropertyGroup>
 
   <ItemGroup>
-    <None Remove="PGM\A.txt" />
+    <None Remove="PGM\CALL.txt" />
+    <None Remove="PGM\HELLO.txt" />
   </ItemGroup>
 
   <ItemGroup>
-    <Content Include="PGM\A.txt">
+    <Content Include="PGM\CALL.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+    <Content Include="PGM\HELLO.txt">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
   </ItemGroup>

SVM/VM.cs

@@ -69,14 +69,13 @@ namespace SVM
         {
             if (RUN)
             {
-                //Get op
                 var pc = PC;
                 var instr = instructions[MEM[PC++]];
                 byte[] decoded = instr.Decode(this);
-                Console.WriteLine("A{0} B{1} C{2} D{3}", R[0], R[1], R[2], R[3]);
-                Console.WriteLine("0x{0:X4} {1}", pc, instr.ToASM(decoded));
+                //Console.WriteLine("A{0} B{1} C{2} D{3}", R[0], R[1], R[2], R[3]);
+                //Console.WriteLine("0x{0:X4} {1}", pc, instr.ToASM(decoded));
                 instr.Exec(this, decoded);
-                Console.ReadKey(true);
+                //Console.ReadKey(true);
             }
         }
     }