#include "includes/6551.h"
#include "includes/serial.h"

static void acia_6551_receive_char(unsigned char ch);
static void acia_6551_refresh_ints(void);

struct acia6551
{
	unsigned char transmit_data_register;
	unsigned char receive_data_register;
	unsigned char status_register;
	unsigned char command_register;
	unsigned char control_register;

	/* internal baud rate timer */
	void	*timer;
	/* callback for internal baud rate timer */
	void (*acia_updated_callback)(int id, unsigned long State);

	void	(*irq_callback)(int);

	struct data_form data_form;

	/* receive register */
	struct serial_receive_register	receive_reg;
	/* transmit register */
	struct serial_transmit_register transmit_reg;

	struct serial_connection connection;
};


static struct acia6551 acia;

/*
A1 A0     Write                    Read
 0 0  Transmit Data Register  Receiver Data Register
 0 1  Programmed Reset        Status Register
 1 0              Command Register
 1 1              Control Register
*/

/* called when other side has updated state */
static void acia_6551_in_callback(int id, unsigned long state)
{
	acia.connection.input_state = state;
}


static void	acia_6551_timer_callback(int id)
{
	/* get bit received from other side and update receive register */
	receive_register_update_bit(&acia.receive_reg, get_in_data_bit(acia.connection.input_state));
	
	if (acia.receive_reg.flags & RECEIVE_REGISTER_FULL)
	{
		receive_register_extract(&acia.receive_reg, &acia.data_form);
		acia_6551_receive_char(acia.receive_reg.byte_received);
	}

	/* transmit register full? */
	if ((acia.status_register & (1<<4))==0)
	{
		/* if transmit reg is empty */
		if (acia.transmit_reg.flags & TRANSMIT_REGISTER_EMPTY)
		{
			/* set it up */
			transmit_register_setup(&acia.transmit_reg, &acia.data_form, acia.transmit_data_register);
			/* acia transmit reg now empty */
			acia.status_register |=(1<<4);
			/* and refresh ints */
			acia_6551_refresh_ints();
		}
	}
	
	/* if transmit is not empty... transmit data */
	if ((acia.transmit_reg.flags & TRANSMIT_REGISTER_EMPTY)==0)
	{
	/*	logerror("UART6551\n"); */
		transmit_register_send_bit(&acia.transmit_reg, &acia.connection);
	}
}

void acia_6551_init(void)
{
	serial_helper_setup();

	memset(&acia, 0, sizeof(struct acia6551));
	/* transmit data reg is empty */
	acia.status_register |= (1<<4);
	acia.timer = timer_alloc(acia_6551_timer_callback);

	serial_connection_init(&acia.connection);
	serial_connection_set_in_callback(&acia.connection, acia_6551_in_callback);
	transmit_register_reset(&acia.transmit_reg);
	receive_register_reset(&acia.receive_reg);
}

/* set callback for interrupt request */
void acia_6551_set_irq_callback(void (*callback)(int))
{
	acia.irq_callback = callback;
}

/* update interrupt output */
static void acia_6551_refresh_ints(void)
{
	int interrupt_state;

	interrupt_state = 0;

	/* receive interrupts */

	/* receive data register full? */ 
	if (acia.status_register & (1<<3))
	{
		/* receiver interrupt enable? */
		if ((acia.command_register & (1<<1))==0)
		{
			/* trigger a interrupt */
			interrupt_state = 1;
		}
	}

	/* set state of irq bit in status register */
	acia.status_register &= ~(1<<7);

	if (interrupt_state)
	{
		acia.status_register |=(1<<7);
	}

	if (acia.irq_callback)
        acia.irq_callback(interrupt_state);
}


static void acia_6551_receive_char(unsigned char ch)
{
	/* receive register full? */
	if (acia.status_register & (1<<3))
	{
		/* set overrun error */
		acia.status_register |= (1<<2);
		return;
	}

	/* set new byte */
	acia.receive_data_register = ch;
	/* receive register is full */
	acia.status_register |= (1<<3);
	/* update ints */
	acia_6551_refresh_ints();
}

 READ8_HANDLER(acia_6551_r)
{
	unsigned char data;

	data = 0x0ff;
	switch (offset & 0x03)
	{
		case 0:
		{
			/*  clear parity error, framing error and overrun error */
			/* when read of data reigster is done */
			acia.status_register &=~((1<<0) | (1<<1) | (1<<2));
			/* clear receive data register full flag */
			acia.status_register &=~(1<<3);
			/* return data */
			data = acia.receive_data_register;
		}
		break;

	/*
	Status			          cleared by
	b0	Parity error * (1: error)       self clearing **
	b1	Framing error * (1: error)      self clearing **
	b2	Overrun * (1: error)            self clearing **
	b3	Receive Data Register Full (1: full)  Read Receive Data Register
	b4	Transmit Data Reg Empty (1: empty) Write Transmit Data Register
	b5	DCD (0: DCD low, 1: DCD high) Not resettable, reflects DCD state
	b6	DSR (0: DSR low, 1: DCD high) Not resettable, reflects DSR state
	b7	IRQ (0: no int., 1: interrupt)  Read Status Register
    */
		case 1:
        {
            data = acia.status_register;
			/* clear interrupt */
			acia.status_register &= ~(1<<7);
		}
        break;

        case 2:
			data = acia.command_register;
			break;

		case 3:
			data = acia.control_register;
			break;

		default:
			break;
	}

	logerror("6551 R %04x %02x\n",offset & 0x03,data);

	return data;
}

static void acia_6551_update_data_form(void)
{
	acia.data_form.word_length = 8-((acia.control_register>>5) & 0x03);
	acia.data_form.stop_bit_count = (acia.control_register>>7)+1;

	if (acia.command_register & (1<<5))
	{
		acia.data_form.parity = SERIAL_PARITY_ODD;
	}
	else
	{
		acia.data_form.parity = SERIAL_PARITY_NONE;
	}

	receive_register_setup(&acia.receive_reg, &acia.data_form);
}


WRITE8_HANDLER(acia_6551_w)
{
	logerror("6551 W %04x %02x\n",offset & 0x03, data);

	switch (offset & 0x03)
	{
		case 0:
		{
			/* clear transmit data register empty */
			acia.status_register &= ~(1<<4);
			/* store byte */
			acia.transmit_data_register = data;

		}
		break;

		case 1:
		{
			/* telstrat writes 0x07f! */		
		}
		break;


		/* 
		Command Register:

		b0	Data Terminal Ready
			0 : disable receiver and all interrupts (DTR high)
			1 : enable receiver and all interrupts (DTR low)
		b1	Receiver Interrupt Enable
			0 : IRQ interrupt enabled from bit 3 of status register
			1 : IRQ interrupt disabled
		b3,b2	Transmitter Control
				Transmit Interrupt    RTS level    Transmitter
			00	   disabled		high		off
			01	   enabled		low		on
			10	   disabled		low		on
			11	   disabled		low	   Transmit BRK
		b4	Normal/Echo Mode for Receiver
			0 : normal
			1 : echo (bits 2 and 3 must be 0)
		b5	Parity Enable
			0 : parity disabled, no parity bit generated or received
			1 : parity enabled
		b7,b6	Parity
			00 : odd parity receiver and transmitter
			01 : even parity receiver and transmitter
			10 : mark parity bit transmitted, parity check disabled
			11 : space parity bit transmitted, parity check disabled
		*/

		case 2:
		{
			acia.command_register = data;

			/* update state of dtr */
			acia.connection.State &=~SERIAL_STATE_DTR;
			if (acia.command_register & (1<<0))
			{
				acia.connection.State |=SERIAL_STATE_DTR;
			}

			/* update state of rts */
			switch ((acia.command_register>>2) & 0x03)
			{
				case 0:
				{
					acia.connection.State &=~SERIAL_STATE_RTS;
				}
				break;
				
				case 1:
				case 2:
				case 3:
				{
					acia.connection.State |=SERIAL_STATE_RTS;
				}
				break;
			}

			serial_connection_out(&acia.connection);

			acia_6551_update_data_form();
		}
		break;

		/*
		Control register:

		b3-b0	baud rate generator:
			0000 : 16x external clock
			0001 : 50 baud
			0010 : 75 25
			0011 : 110 35
			0100 : 134.5
			0101 : 150
			0110 : 300 150
			0111 : 600 300
			1000 : 1200	600
			1001 : 1800	600
			1010 : 2400 600
			1011 : 3600 1200
			1100 : 4800 1200
			1101 : 7200 2400
			1110 : 9600 2400
			1111 : 19,200 9600
		b4	receiver clock source
			0 : external receiver clock
			1 : baud rate generator
		b6,b5	word length
			00 : 8 bits
			01 : 7
			10 : 6
			11 : 5
		b7	stop bits
			0 : 1 stop bit
			1 : 2 stop bits
			    (1 stop bit if parity and word length = 8)
			    (1 1/2 stop bits if word length = 5 and no parity)
		*/
		case 3:
		{
			unsigned char previous_control_register;

            previous_control_register = acia.control_register;
	
            if (((previous_control_register^data) & 0x07)!=0)
			{
				int rate;

                rate = data & 0x07;

				/* baud rate changed? */
				timer_reset(acia.timer, TIME_NEVER);

				if (rate==0)
				{
					/* 16x external clock */
					logerror("6551: external clock not supported!\n");
				}
				else
				{
					int baud_rate;

					switch (rate)
					{
						
						default:
						case 1:
						{
							baud_rate = 50;
						}
						break;
						
						case 2:
						{
							baud_rate = 75;
						}
						break;

						case 3:
						{
							baud_rate = 110;
						}
						break;

						case 4:
						{
							baud_rate = 135;
						}
						break;
						
						case 5:
						{
							baud_rate = 150;
						}
						break;						
						
						case 6:
						{
							baud_rate = 300;
						}
						break;

						case 7:
						{
							baud_rate = 600;
						}
						break;	
						
						case 8:
						{
							baud_rate = 1200;
						}
						break;						
						
						case 9:
						{
							baud_rate = 1800;
						}
						break;						
						
						case 10:
						{
							baud_rate = 2400;
						}
						break;

						case 11:
						{
							baud_rate = 3600;
						}
						break;
						
						case 12:
						{
							baud_rate = 4800;
						}
						break;
			
						case 13:
						{
							baud_rate = 7200;
						}
						break;
			
						case 14:
						{
							baud_rate = 9600;
						}
						break;
			
						case 15:
						{
							baud_rate = 19200;
						}
						break;
					}

					timer_adjust(acia.timer, 0, 0, TIME_IN_HZ(baud_rate));
				}
			}

			acia.control_register = data;
			acia_6551_update_data_form();
		}
		break;

		default:
			break;
	}

}


void acia_6551_connect_to_serial_device(mess_image *image)
{
	serial_device_connect(image, &acia.connection);
}
