//
// ds1305.c is a file that contains functions for dealing with the ds1305
// timekeeping chip from Dallas Semiconductor. The device has a real time
// clock calendar, plus about 96 bytes of non-volatile RAM. The device 
// uses an SPI interface.
//
// This file contains routines required to read and write the ds1305. 
//
// The major functions in this file are the ReadBlock and WriteBlock routines.
// plus an Init routine.
//
// The original version of this file assumes that the SPI device is connected
// to the SPI bus, but the chip select line is found on PORTB pin 0
//
// To change the chip select line, you only need to change the two routines
// ds1305_spi_select and ds1305_spi_deselect.
//
// This file is fairly straight forward ANSI C, though it does use the C++ 
// end of line comment style. It was compiled using the Imagecraft C compiler,
// and should be portable between the 68HC11 and the 68HC12 CPU's. 
//
// Created: 4/30/2000 kevinro@kevinro.com
//
// See the companion article for this code at 
// www.seattlerobotics.org/encoder/200005/ds1305.html 
//

#include <hc11.h>
#include "ds1305.h"

//
// This routine selects the ds1305 device. Must be called
// before transferring data to the SPI port
//
// This assumes the ds1305 is connected to PORTB:0
//
// Need to insure that this is CPHA = 1 due to the 
// timing requirements of the part. If the SPI bus is shared
// with other devices, their Select routines should reset these
// parameters to their value.
// Raising the line enables the part

void ds1305_spi_select() {
	SPCR = SPCR | 0x04; 
	PORTB = PORTB | 0x01;
}

//
// This routine deselects the device by lowering the CE
// line. Must be done after the xfer is complete
//
void ds1305_spi_deselect() { 
	PORTB = PORTB & 0xFE; 
}

//
// This INIT routine sets up PORTD:SS to be an output pin
// which disables the mode-fault detection circuit. It
// also sets up the SPI system for CPOL = 0, CPHA = 1
//
void ds1305_Init()
{
	PORTD = PORTD | 0x38;
	DDRD = DDRD | 0x38;
		
	ds1305_spi_deselect();
	
	SPCR = 0x54;
}

// This routine exchanges 1 byte with the SPI port. 
unsigned char ds1305_spi_xfer(unsigned char cByte)
{
	SPDR = cByte;
	while ((SPSR & 0x80) == 0);
	return SPDR;
}
//
// ReadBlock reads iCount bytes starting at cAddr into the
// buffer pBuffer
//
void ds1305_ReadBlock(unsigned char cAddr, unsigned char *pBuffer, unsigned int iCount)
{
	ds1305_spi_select();
	ds1305_spi_xfer(cAddr);
	while(iCount--)
	{
		*pBuffer++ = ds1305_spi_xfer(0);
	}
	ds1305_spi_deselect();
}

//
// WriteBlock sends iCount bytes from the buffer pBuffer
// to the device at iAddr + 0x80. The device uses a split
// memory map where all write addresses are at address +0x80
//
void ds1305_WriteBlock(unsigned char iAddr, unsigned char *pBuffer, unsigned int iCount)
{
	ds1305_spi_select();
	ds1305_spi_xfer(iAddr + 0x80);
	while(iCount--)
	{
		 ds1305_spi_xfer(*pBuffer++);
	}
	ds1305_spi_deselect();
}