//   entire available packet buffer space is allocated
#define TXSTART_INIT   	0x40
#define RXSTART_INIT   	0x46
#define RXSTOP_INIT    	0x60



void rtl8019BeginPacketSend(unsigned int packetLength)
{
	unsigned int sendPacketLength;
	sendPacketLength = (packetLength>=ETHERNET_MIN_PACKET_LENGTH) ?
	                 packetLength : ETHERNET_MIN_PACKET_LENGTH ;
	
	//start the NIC
	rtl8019Write(CR,0x22);
	
	// still transmitting a packet - wait for it to finish
	while( rtl8019Read(CR) & 0x04 );

	//load beginning page for transmit buffer
	rtl8019Write(TPSR,TXSTART_INIT);
	
	//set start address for remote DMA operation
	rtl8019Write(RSAR0,0x00);
	rtl8019Write(RSAR1,0x40);
	
	//clear the packet stored interrupt
	rtl8019Write(ISR,(1<<ISR_PTX));

	//load data byte count for remote DMA
	rtl8019Write(RBCR0, (unsigned char)(packetLength));
	rtl8019Write(RBCR1, (unsigned char)(packetLength>>8));

	rtl8019Write(TBCR0, (unsigned char)(sendPacketLength));
	rtl8019Write(TBCR1, (unsigned char)((sendPacketLength)>>8));
	
	//do remote write operation
	rtl8019Write(CR,0x12);
}



void rtl8019SendPacketData(unsigned char * localBuffer, unsigned int length)
{
	unsigned int i;
	
	for(i=0;i<length;i++)
		rtl8019Write(RDMAPORT, localBuffer[i]);
}



void rtl8019EndPacketSend(void)
{
	//send the contents of the transmit buffer onto the network
	rtl8019Write(CR,0x24);
	
	// clear the remote DMA interrupt
	rtl8019Write(ISR, (1<<ISR_RDC));
}




// pointers to locations in the RTL8019 receive buffer
static unsigned char nextPage;
static unsigned int currentRetreiveAddress;

// location of items in the RTL8019's page header
#define  enetpacketstatus     0x00
#define  nextblock_ptr        0x01
#define	 enetpacketLenL		  0x02
#define	 enetpacketLenH		  0x03

unsigned int rtl8019BeginPacketRetreive(void)
{
	unsigned char i;
	unsigned char bnry;
	
	unsigned char pageheader[4];
	unsigned int rxlen;
	
	// check for and handle an overflow
	rtl8019ProcessInterrupt();
	
	// read CURR from page 1
	rtl8019Write(CR,0x62);
	i = rtl8019Read(CURR);
	
	// return to page 0
	rtl8019Write(CR,0x22);
	
	// read the boundary register - pointing to the beginning of the packet
	bnry = rtl8019Read(BNRY) ;
	
	// return if there is no packet in the buffer
	if( bnry == i )
		return 0;
	

	// clear the packet received interrupt flag
	rtl8019Write(ISR, (1<<ISR_PRX));
	
	// the boundary pointer is invalid, reset the contents of the buffer and exit
	if( (bnry >= RXSTOP_INIT) || (bnry < RXSTART_INIT) )
	{
		rtl8019Write(BNRY, RXSTART_INIT);
		rtl8019Write(CR, 0x62);
		rtl8019Write(CURR, RXSTART_INIT);
		rtl8019Write(CR, 0x22);
		
		return 0;
	}

	// initiate DMA to transfer the RTL8019 packet header
    rtl8019Write(RBCR0, 4);
    rtl8019Write(RBCR1, 0);
    rtl8019Write(RSAR0, 0);
    rtl8019Write(RSAR1, bnry);
    rtl8019Write(CR, 0x0A);
	for(i=0;i<4;i++)
		pageheader[i] = rtl8019Read(RDMAPORT);
	
	// end the DMA operation
    rtl8019Write(CR, 0x22);
    for(i = 0; i <= 20; i++)
        if(rtl8019Read(ISR) & 1<<6)
            break;
    rtl8019Write(ISR, 1<<6);

	
	rxlen = (pageheader[enetpacketLenH]<<8) + pageheader[enetpacketLenL];
	nextPage = pageheader[nextblock_ptr] ;
	
	currentRetreiveAddress = (bnry<<8) + 4;
	
	// if the nextPage pointer is invalid, the packet is not ready yet - exit
	if( (nextPage >= RXSTOP_INIT) || (nextPage < RXSTART_INIT) )
		return 0;
    
    return rxlen-4;
}


void rtl8019RetreivePacketData(unsigned char * localBuffer, unsigned int length)
{
	unsigned int i;
	
	// initiate DMA to transfer the data
    rtl8019Write(RBCR0, (unsigned char)length);
    rtl8019Write(RBCR1, (unsigned char)(length>>8));
    rtl8019Write(RSAR0, (unsigned char)currentRetreiveAddress);
    rtl8019Write(RSAR1, (unsigned char)(currentRetreiveAddress>>8));
    rtl8019Write(CR, 0x0A);
	for(i=0;i<length;i++)
		localBuffer[i] = rtl8019Read(RDMAPORT);

	// end the DMA operation
    rtl8019Write(CR, 0x22);
    for(i = 0; i <= 20; i++)
        if(rtl8019Read(ISR) & 1<<6)
            break;
    rtl8019Write(ISR, 1<<6);
    
    currentRetreiveAddress += length;
    if( currentRetreiveAddress >= 0x6000 )
    	currentRetreiveAddress = currentRetreiveAddress - (0x6000-0x4600) ;
}



void rtl8019EndPacketRetreive(void)
{
	unsigned char i;

	// end the DMA operation
    rtl8019Write(CR, 0x22);
    for(i = 0; i <= 20; i++)
        if(rtl8019Read(ISR) & 1<<6)
            break;
    rtl8019Write(ISR, 1<<6);

	// set the boundary register to point to the start of the next packet
    rtl8019Write(BNRY, nextPage);
}


void rtl8019Overrun(void)
{
	unsigned char data_L, resend;	

	data_L = rtl8019Read(CR);
	rtl8019Write(CR, 0x21);
	delay_ms(2);
	rtl8019Write(RBCR0, 0x00);
	rtl8019Write(RBCR1, 0x00);
	if(!(data_L & 0x04))
		resend = 0;
	else if(data_L & 0x04)
	{
		data_L = rtl8019Read(ISR);
		if((data_L & 0x02) || (data_L & 0x08))
	    	resend = 0;
	    else
	    	resend = 1;
	}
	
	rtl8019Write(TCR, 0x02);
	rtl8019Write(CR, 0x22);
	rtl8019Write(BNRY, RXSTART_INIT);
	rtl8019Write(CR, 0x62);
	rtl8019Write(CURR, RXSTART_INIT);
	rtl8019Write(CR, 0x22);
	rtl8019Write(ISR, 0x10);
	rtl8019Write(TCR, TCR_INIT);
	
    if(resend)
        rtl8019Write(CR, 0x26);

    rtl8019Write(ISR, 0xFF);
}


void rtl8019Init(void)
{
	rtl8019SetupPorts();
	
	HARD_RESET_RTL8019();
	
	// do soft reset
	rtl8019Write( ISR, rtl8019Read(ISR) ) ;
	delay_ms(50);

    // switch to page 3 to load config registers
    rtl8019Write(CR, 0xE1);

    // disable EEPROM write protect of config registers
    rtl8019Write(RTL_EECR, 0xC0);

    // set network type to 10 Base-T link test
    rtl8019Write(CONFIG2, 0x20);

    // disable powerdown and sleep
    rtl8019Write(CONFIG3, 0);
    delay_ms(255);

    // reenable EEPROM write protect
    rtl8019Write(RTL_EECR, 0);

    // go back to page 0
    rtl8019Write(CR, 0x21);

    rtl8019Write(CR,0x21);       // stop the NIC, abort DMA, page 0
	delay_ms(2);               // make sure nothing is coming in or going out
	rtl8019Write(DCR, DCR_INIT);    // 0x58
	rtl8019Write(RBCR0,0x00);
	rtl8019Write(RBCR1,0x00);
	rtl8019Write(RCR,0x04);
	rtl8019Write(TPSR, TXSTART_INIT);
	rtl8019Write(TCR,0x02);
	rtl8019Write(PSTART, RXSTART_INIT);
	rtl8019Write(BNRY, RXSTART_INIT);
	rtl8019Write(PSTOP, RXSTOP_INIT);
	rtl8019Write(CR, 0x61);
	delay_ms(2);
	rtl8019Write(CURR, RXSTART_INIT);
	
	rtl8019Write(PAR0+0, MYMAC_0);
	rtl8019Write(PAR0+1, MYMAC_1);
	rtl8019Write(PAR0+2, MYMAC_2);
	rtl8019Write(PAR0+3, MYMAC_3);
	rtl8019Write(PAR0+4, MYMAC_4);
	rtl8019Write(PAR0+5, MYMAC_5);
     	  
	rtl8019Write(CR,0x21);
	rtl8019Write(DCR, DCR_INIT);
	rtl8019Write(CR,0x22);
	rtl8019Write(ISR,0xFF);
	rtl8019Write(IMR, IMR_INIT);
	rtl8019Write(TCR, TCR_INIT);
	
	rtl8019Write(CR, 0x22);	// start the NIC
}


void rtl8019ProcessInterrupt(void)
{
	unsigned char byte = rtl8019Read(ISR);
	
	if( byte & (1<<ISR_OVW) )
		rtl8019Overrun();
}