cygnal_i2c_example_program.c

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//------------------------------------------------------------------------------
// Keil Software, Inc.
// 
// Project: 	Cygnal 8051F000 I2C Example Program
//
// Filename: 	Cygnal_I2C_Example_Program.c
// Version: 	1.0.0
// Description:	This file contains example code that will communicate to a 
//				serial EEPROM using I2C.  Data will be printed over the
//				serial port.
//
// Copyright 2000 - Keil Software, Inc.
// All rights reserved.
//------------------------------------------------------------------------------

//------------------------------------------------------------------------------
// Header files
//------------------------------------------------------------------------------
#include <REG51F0X0.H> 						// Header file for the Cygnal 8051F0X0
#include <STDIO.H> 							// Header file for standard I/O

//------------------------------------------------------------------------------
// Value Definitions
//------------------------------------------------------------------------------
#define 	TRUE			0x01			// Value representing TRUE
#define		FALSE			0x00			// Value representing FALSE
#define 	ON				0x01			// Value representing ON
#define		OFF				0x00			// Value representing OFF
#define 	HIGH			0x01			// Value representing ON
#define		LOW				0x00			// Value representing OFF

#define  	DELAY_WRITE		5000			// approx. 5 ms delay write time (about 1000 cycles / ms)
#define  	DELAY_BLINK		50000			// Value for delay time - blink 

//------------------------------------------------------------------------------
// Macros
//------------------------------------------------------------------------------
											// Get high byte macro
#define high_byte(x)		((x & 0xFF00) >> 8)

//------------------------------------------------------------------------------
// I/O Port Defines
//------------------------------------------------------------------------------
sbit  		P1_6 		= 	0x96;			// Define the individual bit (P1.6)
#define 	LED				P1_6			// The eval board has an LED on P1.6

//------------------------------------------------------------------------------
// I2C Bus (SMBus) register bit definitions
//------------------------------------------------------------------------------
sbit		BUS_BUSY	=	0xC7;			// SM Bus Busy (bit 7)
sbit		BUS_EN		=	0xC6;			// SM Bus Enable (bit 6)
sbit		BUS_START	=	0xC5;			// SM Bus Start (bit 5)
sbit		BUS_STOP	=	0xC4;			// SM Bus Stop (bit 4)
sbit		BUS_INT		=	0xC3;			// SM Bus Interrupt (bit 3)
sbit		BUS_AA		=	0xC2;			// SM Bus ACK (bit 2)
sbit		BUS_FTE		=	0xC1;			// SM Bus Clock timeout - high (bit 1)
sbit		BUS_TOE		=	0xC0;			// SM Bus Clock timeout - low (bit 0)

//------------------------------------------------------------------------------
// Rerserve Interrupt vector space (the 8051F000 has an IV table from 0x03 to 0xAB)
//------------------------------------------------------------------------------
unsigned char code iv_table [0xB0] _at_ 0x0003;

//------------------------------------------------------------------------------
// Function Prototypes
//------------------------------------------------------------------------------
void write_byte (unsigned char data_out, unsigned int address);
unsigned char read_byte (unsigned int address);
void i2c_write (unsigned char output_data);
unsigned char i2c_read (void);
void delay_time (unsigned int time_end);
void i2c_start (void);
unsigned char  i2c_stop_and_read (void);
void repeated_i2c_start_and_write (unsigned char output_data);
void i2c_stop_and_write (unsigned char output_data);

//------------------------------------------------------------------------------
// MAIN FUNCTION 
//------------------------------------------------------------------------------
void main (void)
{
	unsigned int eeprom_address;
	unsigned char eeprom_data;	

	// Disable the WDT (page 93 of data sheet)
	WDTCN = 0xDE;
	WDTCN = 0xAD;

	// Set internal oscilator to 16 MHz - Startup is 2 MHz (page 98 of data sheet)
	OSCICN = 0x07;


	// On the Cygnal processor there is a "Crossover" network that must	
	// be initialized to establish the port pin assignements
	// (see page 101 of the data sheet)
	XBR0 = 0x05;							// Set UART and SMBus to be enabled
	XBR1 = 0x00;							// No functions routed in this register
	XBR2 = 0x40;							// Pull-ups enabled, XBAR enabled, no ADC

	PRT1CF = 0x40;							// Set port 1.6 to push/pull 
											// (i.e the LED on the Eval board)

	// Initialize the serial port (9600, 8, N, 1)      
	PCON &= 0x7F;							// Clear bit 7 of the PCON register (SMOD1 = 0)  
	SCON = 0x50;							// 0101,0000 (Mode 1 and RxD enable)			
	CKCON = 0x10;							// Make T1M 1 (i.e. SysClk for Timer 1 not / by 12)
											// (see page 141 of the data sheet)

	TMOD |= 0x20;							// Timer #1 in autoreload 8 bit mode
	TCON |= 0x40;							// Set Timer #1 to run mode (TR = 1)
	TH1 = 0xCC;								// Baud rate is determined by
											// Timer #1 overflow rate
											// Baud Rate = (Fcpu / 32) / (256 - TH1)
											// Fcpu = 16.00 MHz (see above setting of osc.)
											// TH1 = 252
											// (see page 130 of the data sheet)

	SCON |= 0x02;							// Set UART to send first char (TI = 1)


	// Initialize the I2C Bus (SMBus)
	// (see page 111)
	SMB0CR = 0x60;							// Set the clock to approx. 10 uS TH, TL (50 kHz) 
											// (see page 117 of the data sheet)
	BUS_EN = TRUE;							// Enable the bus


	printf("\n\rKeil Software, Inc.\n\r");	// Display starup message
	printf("8051F0X0 MCU I睠 Example Test Program\n\r");
	printf("Version 1.0.0\n\r");
	printf("Copyright 2000 - Keil Software, Inc.\n\r");
	printf("All rights reserved.\n\n\r");

	printf("Writing data to EEPROM....");

	for (eeprom_address = 0; eeprom_address < 75; eeprom_address++)
		write_byte((unsigned char)eeprom_address + 0x30, eeprom_address);

	printf("Done!\r\n\n");


	while (TRUE)
	{
		for (eeprom_address = 0; eeprom_address < 75; eeprom_address++)
		{
											// Read data from eeprom and display it
			eeprom_data = read_byte(eeprom_address);
			printf("Address: %3u	Character: %c\n\r", eeprom_address, eeprom_data);

			LED = HIGH;						// Blink LED with delay
			delay_time(DELAY_BLINK);

			LED = LOW;
			delay_time(DELAY_BLINK);
		}
	}
}

//------------------------------------------------------------------------------
// I2C Peripheral Function Prototypes
//------------------------------------------------------------------------------

//------------------------------------------------------------------------------
// Procedure:	write_byte
// Inputs:		data out, address
// Outputs:		none
// Description:	Writes a byte to the EEPROM given the address 
//------------------------------------------------------------------------------
void write_byte (unsigned char data_out, unsigned int address)
{
	i2c_start();							// Send start signal
   	i2c_write(0xA0);              			// Send identifier I2C address
   	i2c_write(high_byte(address)); 			// Send address to EEPROM
   	i2c_write((unsigned char)address);  	// Send address to EEPROM
   	i2c_stop_and_write(data_out);      		// Send low byte to EEPROM
   	delay_time(DELAY_WRITE);       			// Delay a period of time to write
}

//------------------------------------------------------------------------------
// Procedure:	read_byte
// Inputs:		address
// Outputs:		none
// Description:	Reads a byte from the EEPROM given the address 
//------------------------------------------------------------------------------
unsigned char read_byte (unsigned int address)
{
   	unsigned char data_in;

	i2c_start();							// Send start signal
  	i2c_write(0xA0);              			// Send identifer I2C address
   	i2c_write(high_byte(address));   		// Send address to EEPROM
											// Send address to EEPROM
											// Send repeated start signal
	repeated_i2c_start_and_write((unsigned char)address);					

   	i2c_write(0xA1);              			// Send identifer I2C address
   	data_in = i2c_stop_and_read();			// Read byte, send stop signal

   	return data_in;                 
}


//------------------------------------------------------------------------------
// 	Routine:	i2c_start
//	Inputs:		none
//	Outputs:	none
//	Purpose:	Sends I2C Start Trasfer - State "B"
//------------------------------------------------------------------------------
void i2c_start (void)
{
	while (BUS_BUSY);						// Wait until we are clear to write
	BUS_START = TRUE;						// Perform I2C start
	while (!BUS_INT);						// Wait until start sent
	BUS_START = FALSE;						// Reset I2C start
	BUS_INT = 0;							// Clear SI
}

//------------------------------------------------------------------------------
// 	Routine:	repeated_i2c_start_and_write
//	Inputs:		none
//	Outputs:	none
//	Purpose:	Sends I2C Start Trasfer - State "B"
//------------------------------------------------------------------------------
void repeated_i2c_start_and_write (unsigned char output_data)
{
	BUS_START = TRUE;						// Perform I2C start
	SMB0DAT = output_data;					// Put data into buffer
	while (!BUS_INT);						// Wait unitl we are done with send
	BUS_INT = 0;							// Clear SI
	BUS_START = FALSE;						// Reset I2C start
	while (!BUS_INT);						// Wait unitl we are done with reset
	BUS_INT = 0;							// Clear SI
}

//------------------------------------------------------------------------------
// 	Routine:	i2c_stop_and_write
//	Inputs:		output byte
//	Outputs:	none
//	Purpose:	Sends I2C Stop Trasfer - State "C" (also sends last byte)
//------------------------------------------------------------------------------
void i2c_stop_and_write (unsigned char output_data)
{
	BUS_STOP = TRUE;						// Perform I2C stop
	SMB0DAT = output_data;					// Put data into buffer
	while (!BUS_INT);						// Wait unitl we are done with send
	BUS_INT = 0;							// Clear SI
}

//------------------------------------------------------------------------------
// 	Routine:	i2c_stop_and_read
//	Inputs:		none
//	Outputs:	input byte
//	Purpose:	Sends I2C Stop Trasfer - State "C" (also reads last byte)
//------------------------------------------------------------------------------
unsigned char i2c_stop_and_read (void)
{
	unsigned char input_data;

	BUS_STOP = TRUE;						// Perform I2C stop
	while (!BUS_INT);						// Wait until we have data to read
	input_data = SMB0DAT;					// Read the data
	BUS_INT = 0;							// Clear SI

	return input_data;
}

//------------------------------------------------------------------------------
// 	Routine:	i2c_write
//	Inputs:		output byte
//	Outputs:	none
//	Purpose:	Writes data over the I2C bus
//------------------------------------------------------------------------------
void i2c_write (unsigned char output_data)
{
	SMB0DAT = output_data;					// Put data into buffer
	while (!BUS_INT);						// Wait unitl we are done with send
	BUS_INT = 0;							// Clear SI
}

//------------------------------------------------------------------------------
// 	Routine:	i2c_read
//	Inputs:		none
//	Outputs:	input byte
//	Purpose:	Reads data from the I2C bus
//------------------------------------------------------------------------------
unsigned char i2c_read (void)
{
	unsigned char input_data;

	while (!BUS_INT);						// Wait until we have data to read
	input_data = SMB0DAT;					// Read the data
	BUS_INT = 0;							// Clear SI

	return input_data;
}



////////////////////////////////////////////////////////////////////////////////
// 	Routine:	delay_time
//	Inputs:		counter value to stop delaying
//	Outputs:	none
//	Purpose:	To pause execution for pre-determined time
////////////////////////////////////////////////////////////////////////////////
void delay_time (unsigned int time_end)
{
	unsigned int index;
	for (index = 0; index < time_end; index++);
}