Software Driver

SST25LF080A 2 Mbit(1M x 8) Serial Flash Memory

February 25th, 2004, Rev. 1.0

ABOUT THE SOFTWARE
This application note provides software driver examples for 25LF080A,
Serial Flash. Extensive comments are included in each routine to describe 
the function of each routine.  The interface coding uses polling method 
rather than the SPI protocol to interface with these serial devices.  The
functions are differentiated below in terms of the communication protocols
(uses Mode 0) and specific device operation instructions. This code has been 
designed to compile using the Keil compiler.


ABOUT THE 25LF080A

Companion product datasheets for the 25LF080A should be reviewed in 
conjunction with this application note for a complete understanding 
of the device.


Device Communication Protocol(pinout related) functions:

Functions                    		Function
------------------------------------------------------------------
init					Initializes clock to set up mode 0.
Send_Byte				Sends one byte using SI pin to send and 
					shift out 1-bit per clock rising edge
Get_Byte				Receives one byte using SO pin to receive and shift 
					in 1-bit per clock falling edge
CE_High					Sets Chip Enable pin of the serial flash to high
CE_Low					Clears Chip Enable of the serial flash to low
Hold_Low				Clears Hold pin to make serial flash hold
Unhold					Unholds the serial flash
WP_Low					Clears WP pin to make serial flash write protected
UnWP					Disables write protection pin

Note:  The pin names of the 25LF080A are used in this application note. The associated test code
will not compile unless these pinouts (SCK, SI, SO, SO, CE, WP, Hold) are pre-defined on your
software which should reflect your hardware interfaced. 	 


Device Operation Instruction functions:

Functions                    		Function
------------------------------------------------------------------
Read_Status_Register			Reads the status register of the serial flash
EWSR					Enables the Write Status Register
WRSR					Performs a write to the status register
WREN					Write enables the serial flash
WRDI					Write disables the serial flash
Read_ID					Reads the manufacturer ID and device ID
Read					Reads one byte from the serial flash and returns byte(max of 20 MHz CLK frequency)
Read_Cont				Reads multiple bytes(max of 20 MHz CLK frequency)
HighSpeed_Read				Reads one byte from the serial flash and returns byte(max of 33 MHz CLK frequency)
HighSpeed_Read_Cont			Reads multiple bytes(max of 33 MHz CLK frequency)
Byte_Program				Program one byte to the serial flash
Auto_Add_IncA				Initial Auto Address Increment process
Auto_Add_IncB				Successive Auto_Address_Increment process after AAI initiation
Chip_Erase				Erases entire serial flash
Sector_Erase				Erases one sector (4 KB) of the serial flash
Block_Erase				Erases one block (32 KB) of the serial flash
Wait_Busy				Polls status register until busy bit is low
Wait_Busy_AAI				Polls status register until busy bit is low for AAI programming
WREN_Check				Checks to see if WEL is set
WREN_AAI_Check				Checks to see if WEL and AAI mode is set


                                                                     
"C" LANGUAGE DRIVERS */

/********************************************************************/
/* Copyright Silicon Storage Technology, Inc. (SST), 1994-2004	    */
/* Example "C" language Driver of 25LF080A Serial Flash		    */
/* Conrado Canio, Silicon Storage Technology, Inc.                  */
/*                                                                  */
/* Revision 1.0, February 25th, 2004			  	    */   
/*                                                                  */
/*								    */
/********************************************************************/

#include <stdio.h>
#include <stdlib.h>


/* Function Prototypes */

void init();
void Send_Byte(unsigned char out);
unsigned char Get_Byte();
void CE_High();
void CE_Low();
void Hold_Low();
void Unhold();
void WP_Low();
void UnWP();
unsigned char Read_Status_Register();
void EWSR();
void WRSR(byte);
void WREN();
void WRDI();
unsigned char Read_ID(ID_addr);
unsigned char Read(unsigned long Dst);
void Read_Cont(unsigned long Dst, unsigned long no_bytes);
unsigned char HighSpeed_Read(unsigned long Dst); 
void HighSpeed_Read_Cont(unsigned long Dst, unsigned long no_bytes);
void Byte_Program(unsigned long Dst, unsigned char byte);
void Auto_Add_IncA(unsigned long Dst, unsigned char byte);
void Auto_Add_IncB(unsigned char byte);
void Chip_Erase();
void Sector_Erase(unsigned long Dst);
void Block_Erase(unsigned long Dst);
void Wait_Busy();
void Wait_Busy_AAI();
void WREN_Check();
void WREN_AAI_Check();

void Verify(unsigned char byte, unsigned char cor_byte);


unsigned char idata upper_128[128];	/* global array to store read data */
					/* to upper RAM area from 80H - FFH */

/************************************************************************/
/* PROCEDURE: init							*/
/*									*/
/* This procedure initializes the SCK to low. Must be called prior to 	*/
/* setting up mode 0.							*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Output:								*/
/*		SCK							*/
/************************************************************************/
void init()
{
	SCK = 0;	/* set clock to low initial state */
}

/************************************************************************/
/* PROCEDURE: Send_Byte							*/
/*									*/
/* This procedure outputs a byte shifting out 1-bit per clock rising	*/
/* edge on the the SI pin(LSB 1st).					*/
/*									*/
/* Input:								*/
/*		out							*/
/*									*/
/* Output:								*/
/*		SI							*/
/************************************************************************/
void Send_Byte(unsigned char out)
{
	
	unsigned char i = 0;
	for (i = 0; i < 8; i++)
	{
		
		if ((out & 0x80) == 0x80)	/* check if MSB is high */
			SI = 1;
		else
			SI = 0;			/* if not, set to low */
		SCK = 1;			/* toggle clock high */
		out = (out << 1);		/* shift 1 place for next bit */
		SCK = 0;			/* toggle clock low */
	}


}

/************************************************************************/
/* PROCEDURE: Get_Byte							*/
/*									*/
/* This procedure inputs a byte shifting in 1-bit per clock falling	*/
/* edge on the SO pin(LSB 1st).						*/
/*									*/
/* Input:								*/
/*		SO							*/
/*									*/
/* Output:								*/
/*		None							*/
/************************************************************************/
unsigned char Get_Byte()
{
	unsigned char i = 0, in = 0, temp = 0;
	for (i = 0; i < 8; i++)
	{
		in = (in << 1);		/* shift 1 place to the left or shift in 0 */
		temp = SO;		/* save input */
		SCK = 1;		/* toggle clock high */
	if (temp == 1)			/* check to see if bit is high */
		in = in | 0x01;		/* if high, make bit high */

		SCK = 0;		/* toggle clock low */

	}
	return in;
}

/************************************************************************/
/* PROCEDURE: CE_High							*/
/*									*/
/* This procedure set CE = High.					*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Output:								*/
/*		CE							*/
/*									*/
/************************************************************************/
void CE_High() 
{
	CE = 1;				/* set CE high */
}


/************************************************************************/
/* PROCEDURE: CE_Low							*/
/*									*/
/* This procedure drives the CE of the device to low.  			*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Output:								*/
/*		CE							*/
/*									*/
/************************************************************************/
void CE_Low() 
{	
	CE = 0;				/* clear CE low */
}



/************************************************************************/
/* PROCEDURE: Hold()							*/
/*									*/
/* This procedure clears the Hold pin to low.				*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Output:								*/
/*		Hold							*/
/************************************************************************/
void Hold_Low()
{
	Hold = 0;			/* clear Hold pin */
}

/************************************************************************/
/* PROCEDURE: Unhold()							*/
/*									*/
/* This procedure sets the Hold pin to high.				*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Output:								*/
/*		Hold							*/
/************************************************************************/
void Unhold()
{
	Hold = 1;			/* set Hold pin */
}

/************************************************************************/
/* PROCEDURE: WP()							*/
/*									*/
/* This procedure clears the WP pin to low.				*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Output:								*/
/*		WP							*/
/************************************************************************/
void WP_Low()
{
	WP = 0;				/* clear WP pin */
}

/************************************************************************/
/* PROCEDURE: UnWP()							*/
/*									*/
/* This procedure sets the WP pin to high.				*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Output:								*/
/*		WP							*/
/************************************************************************/
void UnWP()
{
	WP = 1;				/* set WP pin */
}

/************************************************************************/
/* PROCEDURE: Read_Status_Register					*/
/*									*/
/* This procedure read the status register and returns the byte.	*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Returns:								*/
/*		byte							*/
/************************************************************************/
unsigned char Read_Status_Register()
{
	unsigned char byte = 0;
	CE_Low();			/* enable device */
	Send_Byte(0x05);		/* send RDSR command */
	byte = Get_Byte();		/* receive byte */
	CE_High();			/* disable device */
	return byte;
}

/************************************************************************/
/* PROCEDURE: EWSR							*/
/*									*/
/* This procedure Enables Write Status Register.  			*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Returns:								*/
/*		Nothing							*/
/************************************************************************/
void EWSR()
{
	CE_Low();			/* enable device */
	Send_Byte(0x50);		/* enable writing to the status register */
	CE_High();			/* disable device */
}

/************************************************************************/
/* PROCEDURE: WRSR							*/
/*									*/
/* This procedure writes a byte to the Status Register.			*/
/*									*/
/* Input:								*/
/*		byte							*/
/*									*/
/* Returns:								*/
/*		Nothing							*/
/************************************************************************/
void WRSR(byte)
{
	CE_Low();			/* enable device */
	Send_Byte(0x01);		/* select write to status register */
	Send_Byte(byte);		/* data that will change the status of BPx 
						or BPL (only bits 2,3,7 can be written) */
	CE_High();			/* disable the device */
}

/************************************************************************/
/* PROCEDURE: WREN							*/
/*									*/
/* This procedure enables the Write Enable Latch.			*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Returns:								*/
/*		Nothing							*/
/************************************************************************/
void WREN()
{
	CE_Low();			/* enable device */
	Send_Byte(0x06);		/* send WREN command */
	CE_High();			/* disable device */
}

/************************************************************************/
/* PROCEDURE: WRDI							*/
/*									*/
/* This procedure disables the Write Enable Latch.			*/
/*									*/
/* Input:								*/
/*		None							*/
/*									*/
/* Returns:								*/
/*		Nothing							*/
/************************************************************************/
void WRDI()
{
	CE_Low();			/* enable device */
	Send_Byte(0x04);		/* send WRDI command */
	CE_High();			/* disable device */
}


/************************************************************************/
/* PROCEDURE: Read_ID							*/
/*									*/
/* This procedure Reads the manufacturer's ID and device ID.  It will 	*/
/* use 90h or ABh as the command to read the ID (90h in this sample).   */
/* It is up to the user to give the last byte ID_addr to determine      */
/* whether the device outputs manufacturer's ID first, or device ID 	*/
/* first.  Please see the product datasheet for details.  Returns ID in */
/* variable byte.							*/
/*									*/
/* Input:								*/
/*		ID_addr							*/
/*									*/
/* Returns:								*/
/*		byte:	ID1(Manufacture's ID = BFh or Device ID = 80h)	*/
/*									*/
/************************************************************************/
unsigned char Read_ID(ID_addr)
{
	unsigned char byte;
	CE_Low();			/* enable device */