var memory = Array();
var code = [0xa9, 0x00, 0x20, 0x10, 0x00, 0x4c, 0x02, 0x00, 
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0xe8, 0x88, 0xe6, 0x40, 0x38, 0x69, 0x02, 0x60];
var cycle = 0;
var trace = Array();
var running = false;

function go(n){
	for(var i=0;i<code.length;i++){
		mWrite(i, code[i]);
		setCellValue(i, code[i]);
	}
	mWrite(0xfffc, 0x00);
	mWrite(0xfffd, 0x00);
	steps();
}

function steps(){
	if(running) step();
	setTimeout(steps, 200);
}

function initChip(){
	for(var nn in nodes) nodes[nn].state = 'fl';
	nodes[ngnd].state = 'gnd';
	nodes[npwr].state = 'vcc';
	for(var tn in transistors) transistors[tn].on = false;
	setLow('res');
	setLow('clk0');
	setHigh('rdy'); setLow('so');
	setHigh('irq'); setHigh('nmi');
	recalcNodeList(allNodes()); 
	for(var i=0;i<8;i++){setHigh('clk0'), setLow('clk0');}
	setHigh('res');
	for(var i=0;i<14;i++){step();}
	refresh();
	cycle = 0;
	trace = Array();
	chipStatus();
}

function step(){
	trace[cycle]= {chip: stateString(), mem: getMem()};
	halfStep();
	cycle++;
	chipStatus();
}

function halfStep(){
	var clk = isNodeHigh(nodenames['clk0']);
	if (clk) {setLow('clk0'); handleBusRead(); } 
	else {setHigh('clk0'); handleBusWrite();}
	refresh();
}

function handleBusRead(){
	if(isNodeHigh(nodenames['rw'])) writeDataBus(mRead(readAddressBus()));
}

function handleBusWrite(){
	if(!isNodeHigh(nodenames['rw'])){
		var a = readAddressBus();
		var d = readDataBus();
		mWrite(a,d);
		if(a<0x200) setCellValue(a,d);
	}
}

function readAddressBus(){return readBits('ab', 16);}
function readDataBus(){return readBits('db', 8);}
function readA(){return readBits('a', 8);}
function readY(){return readBits('y', 8);}
function readX(){return readBits('x', 8);}
function readP(){return readBits('p', 8);}
function readSP(){return readBits('s', 8);}

function readBits(name, n){
	var res = 0;
	for(var i=0;i<n;i++){
		var nn = nodenames[name+i];
		res+=((isNodeHigh(nn))?1:0)<<i;
	}
	return res;
}

function writeDataBus(x){
	var recalcs = Array();
	for(var i=0;i<8;i++){
		var nn = nodenames['db'+i];
		var n = nodes[nn];
		if((x%2)==0) {n.pulldown=true; n.pullup=false;}
		else {n.pulldown=false; n.pullup=true;}
		recalcs.push(nn);
		x>>=1;
	}
	recalcNodeList(recalcs);
}

function mRead(a){
	if(memory[a]==undefined) return 0;
	else return memory[a];
}

function mWrite(a, d){memory[a]=d;}


function clkNodes(){
	var res = Array();
	res.push(943);
	for(var i in nodes[943].gates){
		var t = transistors[nodes[943].gates[i]];
		if(t.c1==npwr) res.push(t.c2);
		if(t.c2==npwr) res.push(t.c1);
	}
	hiliteNode(res);
}

function runChip(){
	var start = document.getElementById('start');
	var stop = document.getElementById('stop');
	start.style.visibility = 'hidden';
	stop.style.visibility = 'visible';
	running = true;
}

function stopChip(){
	var start = document.getElementById('start');
	var stop = document.getElementById('stop');
	start.style.visibility = 'visible';
	stop.style.visibility = 'hidden';
	running = false;
}

function resetChip(){
	stopChip();
	initChip();
}

function stepForward(){
	stopChip();
	step();
}

function stepBack(){
	if(cycle==0) return;
	showState(trace[--cycle].chip);
	setMem(trace[cycle].mem);
	var clk = isNodeHigh(nodenames['clk0']);
	if(!clk) writeDataBus(mRead(readAddressBus()));
	chipStatus();
}

function chipStatus(){
	var pc = readAddressBus();
	setStatus('PC:', hexWord(pc),
	          'D:', hexByte(readDataBus()), 
	          'SP:',hexByte(readSP()),
	          'cycle:', cycle, '<br>',
	          'A:', hexByte(readA()),
	          'X:', hexByte(readX()),
	          'Y:', hexByte(readY()),
	          'P:', hexByte(readP())
	          );
	selectCell(pc);
}

function getMem(){
	var res = Array();
	for(var i=0;i<0x200;i++) res.push(mRead(i));
	return res;
}

function setMem(arr){
	for(var i=0;i<0x200;i++){mWrite(i, arr[i]); setCellValue(i, arr[i]);}
}

function hexWord(n){return (0x10000+n).toString(16).substring(1)}
function hexByte(n){return (0x100+n).toString(16).substring(1)}