cbus.c

CML CMX868 modem

//---------------------------------------------------------------------------------------------------
//	Project:-	DE8681
//  	Filename:-	CBUS.C
//	Description:-	SPI interface to CMX868.
//	Programmer:-	D.T.F	
//	Version:-	2.0
//	Created:-	28th February 2002
//	Last modified:- 
//---------------------------------------------------------------------------------------------------
//	(C) Consumer Microcircuits Ltd 2002
//
//	This firmware was designed by:-
//			Consumer Microcircuits Ltd,
//			Langford, Maldon,
//			ESSEX
//			CM9 6WG.
//	in the UK for use with CML evaluation kits only and is based on UK originated technology.
//	Please contact
//			[e-mail]
//			[phone]
//	for licensing details.
//---------------------------------------------------------------------------------------------------

#define CBUS_C

#include	"ef8681.h"

void wr_cbus(unsigned char cbus_addr, unsigned char cbus_byte)
{
	PICCSN = 0;				// Clear CSN

	load_spi(cbus_addr);			// Load CBUS address byte

	load_spi(cbus_byte);			// Load CBUS byte

	PICCSN = 1;				// Set CSN
}

void wr16_cbus(unsigned char cbus_addr, unsigned int cbus_word)
{
	PICCSN = 0;				// Clear CSN

	load_spi(cbus_addr);			// Load CBUS address byte

	load_spi((cbus_word >> 8) & 0xFF);	// Load CBUS MS byte

	load_spi(cbus_word & 0xFF);		// Load CBUS LS byte

	PICCSN = 1;				// Set CSN
}

unsigned char rd_cbus(unsigned char cbus_addr)
{
	unsigned char cbus_byte;

	PICCSN = 0;				// Clear CSN

	load_spi(cbus_addr);			// Load CBUS address byte

	cbus_byte = load_spi(0x00);		// Read CBUS byte

	PICCSN = 1;				// Set CSN

	return (cbus_byte);			// Return CBUS Byte
}

unsigned int rd16_cbus(unsigned char cbus_addr)
{
	unsigned int cbus_word;

	unsigned char cbus_lsbyte,cbus_msbyte;

	PICCSN = 0;				// Clear CSN

	load_spi(cbus_addr);			// Load CBUS address byte

	cbus_msbyte = load_spi(0x00);		// Read CBUS MS byte

	cbus_lsbyte = load_spi(0x00);		// Read CBUS MS byte

	PICCSN = 1;				// Set CSN

	cbus_word = ((cbus_msbyte & 0xFF) << 8) | (cbus_lsbyte & 0xFF); 

	return (cbus_word);			// Return CBUS Word
}

void reset_cbus()
{
	PICCSN = 0;				// Clear CSN

	load_spi(CMXGENRESET);			// Load general reset byte

	PICCSN = 1;				// Set CSN

// Clear CMX868 write shadow registers
	CMXGENCTRL = 0;
	CMXTXMODE = 0;
	CMXRXMODE = 0;
	CMXTXDATA = 0;
	CMXTXDATAV14 = 0;
	CMXPROG = 0;
	CMXTESTADDR = 0;
	CMXTESTWR = 0;
}

void pwrup()
{
	XTAL = USER_XTAL;			// Ensure correct CMX868 Xtal is selected (S24 Bit 0)
	PWRUP = 1;				// Power Up CMX868
	RESET = 1;				// Initially hold internal circuitry in reset condition 
	wr16_cbus(CMXGENCTRL_ADDR,CMXGENCTRL);	// Update CBUS register

	DelayMs(20);				// 20ms Power Up Delay

	RESET = 0;				// Normal Operation
	wr16_cbus(CMXGENCTRL_ADDR,CMXGENCTRL);	// Update CBUS register
}

unsigned char load_spi(unsigned char loadvalue)
{
	SSPBUF = loadvalue;

	while(!SSPIF)				// Wait until SSP interrupt flag is clear
		continue;

	SSPIF = 0;				// Clear SSP interrupt flag
	return(SSPBUF);
}

void init_spi()
{
	SSPCON = 0;	// SSPM3:SSPM0=0, SPI Master Mode, Clock=Fosc/4.
	CKP = 0;	// Idle state for clock is LO
	STAT_CKE = 1;	// With CKP = 0 and CKE = 1 data transmitted on rising edge
	SSPEN = 1;	// Enables serial port and configures SCK, SDO and SDI as serial port pins.
	SSPIF = 0;	// Clear SSP interrupt flag
}