Tag Archives: source

MP08E Emulator Source Code

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Hello everyone, here is the source code of the emulator introduced during my workshop concerning emulators. I waited almost two weeks to publish the code in order to let people to try to build it by themselves.

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MP08ALib;
 
namespace MP08AEmu
{
    public enum STATUS_FLAGS { EQUAL = 0, GREATER = 1, LOWER = 2 };
 
    public class MP08E : ICPU
    {
        byte[] memory = new byte[0x100];
 
        protected byte AC;
        protected byte[] dataRegisters = new byte[0x10];
        protected byte flags;
        protected byte PC;
        protected byte latch;
 
        public byte[] GetMemory() { return memory; }
 
        public void LoadMemory(byte[] buffer)
        {
            for (int i = 0; i < buffer.Length; i++)
                this.memory[i] = buffer[i];
        }
 
        public void Reset()
        {
            this.AC = 0;
            this.flags = 0;
            this.PC = 0;
            this.latch = 0;
            dataRegisters = new byte[0x10];
        }
 
        public void Step()
        {
            byte opcode = (byte)((memory[this.PC] >> 4)  & 0xF);
            byte imm4 = (byte)(memory[this.PC] & 0xF);
            byte imm8 = (byte)(memory[(this.PC + 1) & 0xFF]);
            bool jmp = false;
 
            switch (opcode)
            {
                case 0x0: break;																	            /* NOP */
                case 0x1: this.AC = memory[++this.PC]; break;                                                   /* LOADLIT */
                case 0x2: this.AC = dataRegisters[imm4]; break;									                /* LOADREG */
                case 0x3: dataRegisters[imm4] = this.AC; break;									                /* STORE */
                case 0x4: this.AC++; break;                                                                     /* INC */
                case 0x5: this.AC--; break;	                                                                    /* DEC */
                case 0x6: this.AC = latch; break;		            							                /* IN */
                case 0x7: this.latch = this.AC; break;									                        /* OUT */
                case 0x8: Compare(this.AC, imm8); this.PC++; break;									            /* COMPLIT */
                case 0x9: Compare(this.AC, dataRegisters[imm4]); break;									        /* COMPREG */
                case 0xA: if (GetBit(flags, STATUS_FLAGS.EQUAL)) { this.PC = imm8; jmp = true; } break;			/* JE addr */
                case 0xB: if (GetBit(flags, STATUS_FLAGS.GREATER)) { this.PC = imm8; jmp = true; } break;		/* JG addr */
                case 0xC: if (GetBit(flags, STATUS_FLAGS.LOWER)) { this.PC = imm8; jmp = true; } break;			/* JL addr */
                case 0xD: this.PC = imm8; jmp = true; break;									            	/* JMP addr */
                case 0xE: this.AC = (byte)(this.AC + dataRegisters[imm4]); break;				                /* ADD reg */
                case 0xF: this.flags = 0; break;				                                                /* CLEAR */
            }
 
            if (!jmp)
                this.PC++;
        }
 
        public bool GetBit(int value, int bit) { return (((value >> bit) & 0x1) == 1); }
        public bool GetBit(int value, STATUS_FLAGS bit) { return GetBit(value, (int)bit); }
 
        public int GetRegister(int reg, int datareg = 0)
        {
            switch (reg)
            {
                case 0: return this.PC;
                case 1: return this.AC;
                case 2: return this.flags;
                case 3: return this.latch;
                case 4: return this.dataRegisters[datareg];
 
                default:
                    return -1;
            }
        }
 
        public void Compare(int ac, int value)
        {
            MP08ALib.Utils.SetBit(ref flags, 0, ac == value);
            MP08ALib.Utils.SetBit(ref flags, 1, ac > value);
            MP08ALib.Utils.SetBit(ref flags, 2, ac < value);
        }
    }
}