src/pit.js - emulators/v86 - Rivoreo Source Code Repositories

 "use strict";

 /**
  * @const
  * In kHz
  */
 var OSCILLATOR_FREQ = 1193.1816666; // 1.193182 MHz

 /**
  * @constructor
  *
  * Programmable Interval Timer
  */
 function PIT(cpu)
 {
     /** @const @type {CPU} */
     this.cpu = cpu;

     this.counter_start_time = new Float64Array(3);
     this.counter_start_value = new Uint16Array(3);

     this.counter_next_low = new Uint8Array(4);
     this.counter_enabled = new Uint8Array(4);
     this.counter_mode = new Uint8Array(4);
     this.counter_read_mode = new Uint8Array(4);

     // 2 = latch low, 1 = latch high, 0 = no latch
     this.counter_latch = new Uint8Array(4);
     this.counter_latch_value = new Uint16Array(3);

     this.counter_reload = new Uint16Array(3);

     // TODO:
     // - counter2 can be controlled by an input

     cpu.io.register_read(0x61, this, function()
     {
         var now = v86.microtick();

         var ref_toggle = (now * (1000 * 1000 / 15000)) & 1;
         var counter2_out = this.did_rollover(2, now);

         return ref_toggle << 4 | counter2_out << 5;
     });

     cpu.io.register_read(0x40, this, function() { return this.counter_read(0); });
     cpu.io.register_read(0x41, this, function() { return this.counter_read(1); });
     cpu.io.register_read(0x42, this, function() { return this.counter_read(2); });

     cpu.io.register_write(0x40, this, function(data) { this.counter_write(0, data); });
     cpu.io.register_write(0x41, this, function(data) { this.counter_write(1, data); });
     cpu.io.register_write(0x42, this, function(data) { this.counter_write(2, data); });

     cpu.io.register_write(0x43, this, this.port43_write);
 }

 PIT.prototype.get_state = function()
 {
     var state = [];

     state[0] = this.counter_next_low;
     state[1] = this.counter_enabled;
     state[2] = this.counter_mode;
     state[3] = this.counter_read_mode;
     state[4] = this.counter_latch;
     state[5] = this.counter_latch_value;
     state[6] = this.counter_reload;
     state[7] = this.counter_start_time;
     state[8] = this.counter_start_value;

     return state;
 };

 PIT.prototype.set_state = function(state)
 {
     this.counter_next_low = state[0];
     this.counter_enabled = state[1];
     this.counter_mode = state[2];
     this.counter_read_mode = state[3];
     this.counter_latch = state[4];
     this.counter_latch_value = state[5];
     this.counter_reload = state[6];
     this.counter_start_time = state[7];
     this.counter_start_value = state[8];
 };

 PIT.prototype.timer = function(now, no_irq)
 {
     var time_to_next_interrupt = 100;

     // counter 0 produces interrupts
     if(!no_irq && this.counter_enabled[0])
     {
         if(this.did_rollover(0, now))
         {
             time_to_next_interrupt = 0;

             this.counter_start_value[0] = this.get_counter_value(0, now);
             this.counter_start_time[0] = now;

             dbg_log("pit interrupt. new value: " + this.counter_start_value[0], LOG_PIT);

             this.cpu.device_raise_irq(0);
             var mode = this.counter_mode[0];

             if(mode === 0)
             {
                 this.counter_enabled[0] = 0;
             }
         }
     }
     time_to_next_interrupt = 0;

     return time_to_next_interrupt;
 };

 PIT.prototype.get_counter_value = function(i, now)
 {
     if(!this.counter_enabled[i])
     {
         return 0;
     }

     var diff = now - this.counter_start_time[i];
     var diff_in_ticks = Math.floor(diff * OSCILLATOR_FREQ);

     var value = this.counter_start_value[i] - diff_in_ticks;

     dbg_log("diff=" + diff + " dticks=" + diff_in_ticks + " value=" + value + " reload=" + this.counter_reload[i], LOG_PIT);

     if(value < 0)
     {
         var reload = this.counter_reload[i];
         value = value % reload + reload;
     }

     return value;
 };

 PIT.prototype.did_rollover = function(i, now)
 {
     var diff = now - this.counter_start_time[i];

     if(diff < 0)
     {
         // should only happen after restore_state
         dbg_log("Warning: PIT timer difference is negative, resetting");
         return true;
     }
     var diff_in_ticks = Math.floor(diff * OSCILLATOR_FREQ);
     //dbg_log(i + ": diff=" + diff + " start_time=" + this.counter_start_time[i] + " diff_in_ticks=" + diff_in_ticks + " (" + diff * OSCILLATOR_FREQ + ") start_value=" + this.counter_start_value[i] + " did_rollover=" + (this.counter_start_value[i] < diff_in_ticks), LOG_PIT);

     return this.counter_start_value[i] < diff_in_ticks;
 };

 PIT.prototype.counter_read = function(i)
 {
     var latch = this.counter_latch[i];

     if(latch)
     {
         this.counter_latch[i]--;

         if(latch === 2)
         {
             return this.counter_latch_value[i] & 0xFF;
         }
         else
         {
             return this.counter_latch_value[i] >> 8;
         }
     }
     else
     {
         var next_low = this.counter_next_low[i];

         if(this.counter_mode[i] === 3)
         {
             this.counter_next_low[i] ^= 1;
         }

         var value = this.get_counter_value(i, v86.microtick());

         if(next_low)
         {
             return value & 0xFF;
         }
         else
         {
             return value >> 8;
         }
     }
 };

 PIT.prototype.counter_write = function(i, value)
 {
     if(this.counter_next_low[i])
     {
         this.counter_reload[i] = this.counter_reload[i] & ~0xFF | value;
     }
     else
     {
         this.counter_reload[i] = this.counter_reload[i] & 0xFF | value << 8;
     }

     if(this.counter_read_mode[i] !== 3 || !this.counter_next_low[i])
     {
         if(!this.counter_reload[i])
         {
             this.counter_reload[i] = 0xFFFF;
         }

         // depends on the mode, should actually
         // happen on the first tick
         this.counter_start_value[i] = this.counter_reload[i];

         this.counter_enabled[i] = true;

         this.counter_start_time[i] = v86.microtick();

         dbg_log("counter" + i + " reload=" + h(this.counter_reload[i]) +
                 " tick=" + (this.counter_reload[i] || 0x10000) / OSCILLATOR_FREQ + "ms", LOG_PIT);
     }

     if(this.counter_read_mode[i] === 3)
     {
         this.counter_next_low[i] ^= 1;
     }
 };

 PIT.prototype.port43_write = function(reg_byte)
 {
     var mode = reg_byte >> 1 & 7,
         binary_mode = reg_byte & 1,
         i = reg_byte >> 6 & 3,
         read_mode = reg_byte >> 4 & 3;

     if(i === 1)
     {
         dbg_log("Unimplemented timer1", LOG_PIT);
     }

     if(i === 3)
     {
         dbg_log("Unimplemented read back", LOG_PIT);
         return;
     }

     if(read_mode === 0)
     {
         // latch
         this.counter_latch[i] = 2;
         var value = this.get_counter_value(i, v86.microtick());
         dbg_log("latch: " + value, LOG_PIT);
         this.counter_latch_value[i] = value ? value - 1 : 0

         return;
     }

     if(mode >= 6)
     {
         // 6 and 7 are aliased to 2 and 3
         mode &= ~4;
     }

     dbg_log("Control: mode=" + mode + " ctr=" + i +
             " read_mode=" + read_mode + " bcd=" + binary_mode, LOG_PIT);

     if(read_mode === 1)
     {
         // msb
         this.counter_next_low[i] = 0;
     }
     else if(read_mode === 2)
     {
         // lsb
         this.counter_next_low[i] = 1;
     }
     else
     {
         // first lsb then msb
         this.counter_next_low[i] = 1;
     }


     if(mode === 0)
     {
     }
     else if(mode === 3 || mode === 2)
     {
         // what is the difference
     }
     else
     {
         dbg_log("Unimplemented counter mode: " + h(mode), LOG_PIT);
     }

     this.counter_mode[i] = mode;
     this.counter_read_mode[i] = read_mode;
 };
	"use strict";

	/**
	* @const
	* In kHz
	*/
	var OSCILLATOR_FREQ = 1193.1816666; // 1.193182 MHz

	/**
	* @constructor
	*
	* Programmable Interval Timer
	*/
	function PIT(cpu)
	{
	/** @const @type {CPU} */
	this.cpu = cpu;

	this.counter_start_time = new Float64Array(3);
	this.counter_start_value = new Uint16Array(3);

	this.counter_next_low = new Uint8Array(4);
	this.counter_enabled = new Uint8Array(4);
	this.counter_mode = new Uint8Array(4);
	this.counter_read_mode = new Uint8Array(4);

	// 2 = latch low, 1 = latch high, 0 = no latch
	this.counter_latch = new Uint8Array(4);
	this.counter_latch_value = new Uint16Array(3);

	this.counter_reload = new Uint16Array(3);

	// TODO:
	// - counter2 can be controlled by an input

	cpu.io.register_read(0x61, this, function()
	{
	var now = v86.microtick();

	var ref_toggle = (now * (1000 * 1000 / 15000)) & 1;
	var counter2_out = this.did_rollover(2, now);

	return ref_toggle << 4 \| counter2_out << 5;
	});

	cpu.io.register_read(0x40, this, function() { return this.counter_read(0); });
	cpu.io.register_read(0x41, this, function() { return this.counter_read(1); });
	cpu.io.register_read(0x42, this, function() { return this.counter_read(2); });

	cpu.io.register_write(0x40, this, function(data) { this.counter_write(0, data); });
	cpu.io.register_write(0x41, this, function(data) { this.counter_write(1, data); });
	cpu.io.register_write(0x42, this, function(data) { this.counter_write(2, data); });

	cpu.io.register_write(0x43, this, this.port43_write);
	}

	PIT.prototype.get_state = function()
	{
	var state = [];

	state[0] = this.counter_next_low;
	state[1] = this.counter_enabled;
	state[2] = this.counter_mode;
	state[3] = this.counter_read_mode;
	state[4] = this.counter_latch;
	state[5] = this.counter_latch_value;
	state[6] = this.counter_reload;
	state[7] = this.counter_start_time;
	state[8] = this.counter_start_value;

	return state;
	};

	PIT.prototype.set_state = function(state)
	{
	this.counter_next_low = state[0];
	this.counter_enabled = state[1];
	this.counter_mode = state[2];
	this.counter_read_mode = state[3];
	this.counter_latch = state[4];
	this.counter_latch_value = state[5];
	this.counter_reload = state[6];
	this.counter_start_time = state[7];
	this.counter_start_value = state[8];
	};

	PIT.prototype.timer = function(now, no_irq)
	{
	var time_to_next_interrupt = 100;

	// counter 0 produces interrupts
	if(!no_irq && this.counter_enabled[0])
	{
	if(this.did_rollover(0, now))
	{
	time_to_next_interrupt = 0;

	this.counter_start_value[0] = this.get_counter_value(0, now);
	this.counter_start_time[0] = now;

	dbg_log("pit interrupt. new value: " + this.counter_start_value[0], LOG_PIT);

	this.cpu.device_raise_irq(0);
	var mode = this.counter_mode[0];

	if(mode === 0)
	{
	this.counter_enabled[0] = 0;
	}
	}
	}
	time_to_next_interrupt = 0;

	return time_to_next_interrupt;
	};

	PIT.prototype.get_counter_value = function(i, now)
	{
	if(!this.counter_enabled[i])
	{
	return 0;
	}

	var diff = now - this.counter_start_time[i];
	var diff_in_ticks = Math.floor(diff * OSCILLATOR_FREQ);

	var value = this.counter_start_value[i] - diff_in_ticks;

	dbg_log("diff=" + diff + " dticks=" + diff_in_ticks + " value=" + value + " reload=" + this.counter_reload[i], LOG_PIT);

	if(value < 0)
	{
	var reload = this.counter_reload[i];
	value = value % reload + reload;
	}

	return value;
	};

	PIT.prototype.did_rollover = function(i, now)
	{
	var diff = now - this.counter_start_time[i];

	if(diff < 0)
	{
	// should only happen after restore_state
	dbg_log("Warning: PIT timer difference is negative, resetting");
	return true;
	}
	var diff_in_ticks = Math.floor(diff * OSCILLATOR_FREQ);
	//dbg_log(i + ": diff=" + diff + " start_time=" + this.counter_start_time[i] + " diff_in_ticks=" + diff_in_ticks + " (" + diff * OSCILLATOR_FREQ + ") start_value=" + this.counter_start_value[i] + " did_rollover=" + (this.counter_start_value[i] < diff_in_ticks), LOG_PIT);

	return this.counter_start_value[i] < diff_in_ticks;
	};

	PIT.prototype.counter_read = function(i)
	{
	var latch = this.counter_latch[i];

	if(latch)
	{
	this.counter_latch[i]--;

	if(latch === 2)
	{
	return this.counter_latch_value[i] & 0xFF;
	}
	else
	{
	return this.counter_latch_value[i] >> 8;
	}
	}
	else
	{
	var next_low = this.counter_next_low[i];

	if(this.counter_mode[i] === 3)
	{
	this.counter_next_low[i] ^= 1;
	}

	var value = this.get_counter_value(i, v86.microtick());

	if(next_low)
	{
	return value & 0xFF;
	}
	else
	{
	return value >> 8;
	}
	}
	};

	PIT.prototype.counter_write = function(i, value)
	{
	if(this.counter_next_low[i])
	{
	this.counter_reload[i] = this.counter_reload[i] & ~0xFF \| value;
	}
	else
	{
	this.counter_reload[i] = this.counter_reload[i] & 0xFF \| value << 8;
	}

	if(this.counter_read_mode[i] !== 3 \|\| !this.counter_next_low[i])
	{
	if(!this.counter_reload[i])
	{
	this.counter_reload[i] = 0xFFFF;
	}

	// depends on the mode, should actually
	// happen on the first tick
	this.counter_start_value[i] = this.counter_reload[i];

	this.counter_enabled[i] = true;

	this.counter_start_time[i] = v86.microtick();

	dbg_log("counter" + i + " reload=" + h(this.counter_reload[i]) +
	" tick=" + (this.counter_reload[i] \|\| 0x10000) / OSCILLATOR_FREQ + "ms", LOG_PIT);
	}

	if(this.counter_read_mode[i] === 3)
	{
	this.counter_next_low[i] ^= 1;
	}
	};

	PIT.prototype.port43_write = function(reg_byte)
	{
	var mode = reg_byte >> 1 & 7,
	binary_mode = reg_byte & 1,
	i = reg_byte >> 6 & 3,
	read_mode = reg_byte >> 4 & 3;

	if(i === 1)
	{
	dbg_log("Unimplemented timer1", LOG_PIT);
	}

	if(i === 3)
	{
	dbg_log("Unimplemented read back", LOG_PIT);
	return;
	}

	if(read_mode === 0)
	{
	// latch
	this.counter_latch[i] = 2;
	var value = this.get_counter_value(i, v86.microtick());
	dbg_log("latch: " + value, LOG_PIT);
	this.counter_latch_value[i] = value ? value - 1 : 0

	return;
	}

	if(mode >= 6)
	{
	// 6 and 7 are aliased to 2 and 3
	mode &= ~4;
	}

	dbg_log("Control: mode=" + mode + " ctr=" + i +
	" read_mode=" + read_mode + " bcd=" + binary_mode, LOG_PIT);

	if(read_mode === 1)
	{
	// msb
	this.counter_next_low[i] = 0;
	}
	else if(read_mode === 2)
	{
	// lsb
	this.counter_next_low[i] = 1;
	}
	else
	{
	// first lsb then msb
	this.counter_next_low[i] = 1;
	}


	if(mode === 0)
	{
	}
	else if(mode === 3 \|\| mode === 2)
	{
	// what is the difference
	}
	else
	{
	dbg_log("Unimplemented counter mode: " + h(mode), LOG_PIT);
	}

	this.counter_mode[i] = mode;
	this.counter_read_mode[i] = read_mode;
	};