change SYS instruction to PORT and add imm4

src/device.h

@@ -0,0 +1,5 @@
+#pragma once
+
+typedef struct {
+
+} Device;

src/emu.h

@@ -5,6 +5,7 @@
 #include <string.h>
 #include <stdbool.h>
 #include "memory.h"
+#include "device.h"
 
 #define FLAG_ZERO (1 << 0)
 #define FLAG_NEGATIVE (1 << 1)

src/instruction.c

@@ -15,7 +15,7 @@ const OperandType INSTRUCTION_OPERAND_TYPES[][3] = {
     {OP_REG, OP_REG,  OP_NONE},   // JIZ
     {OP_REG, OP_REG,  OP_NONE},   // CALL
     {OP_NONE, OP_NONE,  OP_NONE}, // RET
-    {OP_REG, OP_REG,  OP_REG},    // SYS
+    {OP_REG, OP_REG,  OP_IMM4},   // PORT
     {OP_NONE, OP_NONE,  OP_NONE}  // HLT
 };
 
@@ -35,7 +35,7 @@ char* opcodeToCStr(InstructionOpcode opcode) {
         case INST_JIZ:   return "JIZ";
         case INST_CALL:  return "CALL";
         case INST_RET:   return "RET";
-        case INST_SYS:   return "SYS";
+        case INST_PORT:  return "PORT";
         case INST_HLT:   return "HLT";
         default:         return "FIXME";
     }
@@ -81,6 +81,14 @@ char* instructionToCStr(Instruction inst) {
                     registerToCStr(inst.operands[opIdx])
                 );
                 break;
+            case OP_IMM4: 
+                written += snprintf(
+                    buffer + written,
+                    remaining,
+                    "%d",
+                    inst.operands[opIdx]
+                );
+                break;
             case OP_IMM16:
                 written += snprintf(
                     buffer + written,

src/instruction.h

@@ -7,8 +7,8 @@
 
 // -- TYPES -- //
 typedef enum : uint8_t {
-    INST_MOV, INST_MVI, INST_ADD, INST_SUB, INST_LOAD, INST_STORE, INST_AND, INST_OR,
-    INST_XOR, INST_SHF, INST_JMP, INST_JIZ, INST_CALL, INST_RET,   INST_SYS, INST_HLT
+    INST_MOV, INST_MVI, INST_ADD, INST_SUB, INST_LOAD, INST_STORE, INST_AND,  INST_OR,
+    INST_XOR, INST_SHF, INST_JMP, INST_JIZ, INST_CALL, INST_RET,   INST_PORT, INST_HLT
 } InstructionOpcode;
 
 typedef enum {
@@ -38,7 +38,7 @@ typedef struct {
 } Instruction;
 
 typedef enum {
-    OP_NONE, OP_REG, OP_IMM16
+    OP_NONE, OP_REG, OP_IMM4, OP_IMM16
 } OperandType;
 
 // -- CONSTANTS -- //