16bit-cpu.js

/*

## EXPECTED OUTPUT

PC  IR      A   B   C   
1   0x00    0   0   0   
4   0x01    0   5   0   
7   0x01    0   5   1   
10  0x02    1   5   1
13  0x05    1   5   1
7   0x04    1   5   1
10  0x02    2   5   1
13  0x05    2   5   1
7   0x04    2   5   1
10  0x02    3   5   1
13  0x05    3   5   1
7   0x04    3   5   1
10  0x02    4   5   1
13  0x05    4   5   1
7   0x04    4   5   1
10  0x02    5   5   1
16  0x05    5   5   1
17  0x00    5   5   1


*/
var MEM = ['0x00',//---------------- NOP
           '0x01','0x01','0x05',//-- MOV B, 5
           '0x01','0x02','0x01',//-- MOV C, 1
           '0x02','0x00','0x02',//-- ADD A, C
           '0x05','0x00','0x01',//-- IFE A, B
           '0x04','0x07',//--------- JMP 1
           '0x00',//---------------- NOP/\SKIPED
           '0x00'];//--------------- NOP
var PC = 0;
var registers = {
	A : 0,
	B : 0,
	C : 0,
	D : 0
};

var operands = {
	'0x00' : "A",
	'0x01' : "B",
	'0x02' : "C",
	'0x03' : "D"
}

var fetch = function() {
	let A = MEM[PC];
	PC+=1;
	return A;
}

var opcodes = {
	'0x00' : function nop(){}, //NOP
	'0x01' : function mov(){/*MOV R, C*/
		var R = operands[fetch()];
		var c = fetch();
		//console.log(parseInt(c,16));
		registers[R] = parseInt(c,16);
	},
	'0x02' : function add(){ //-- ADD R, r
        var R = operands[fetch()];
        var r = operands[fetch()];
        registers[R] = registers[R] + registers[r];
    },
    "0x03" : function sub(){ //-- SUB R, r
        var R = operands[fetch()];
        var r = operands[fetch()];
        registers[R] = registers[R] - registers[r];
    },
    "0x04" : function jmp(){ //-- JMP addr
        var addr = fetch();
        PC = parseInt(addr,16);
    },
    "0x05" : function ife(){ //-- IFE R, r
        var R = registers[operands[fetch()]];
        var r = registers[operands[fetch()]];
        //PC = (R == r) and PC + 3 or PC
        if (R == r) PC += 3
    }
};



var FDX = function() {
	console.log("PC IR   A B C D")
	while (PC < (MEM.length)){
		var IR = fetch();
		//PC += 1;
		opcodes[IR]();
		console.log(PC+"  "+IR+" "+registers['A']+" "+registers['B']+" "+registers['C']+" "+registers['D']);
	};
};
FDX();