Software Driver

SST25VF040B 4 Mbit(512K x 8) Serial Flash Memory

November 4th, 2005, Rev. 1.0

ABOUT THE SOFTWARE
This application note provides software driver examples for SST25VF040B,
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 SST25VF040B

Companion product datasheets for the SST25VF040B 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
Poll_SO					Used in the polling for RY/BY# of SO during AAI programming
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 SST25VF040B 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
EBSY					Enable SO to output RY/BY# status during AAI programming
DBSY					Disable SO to output RY/BY# status during AAI programming
Read_ID					Reads the manufacturer ID and device ID
Jedec_ID_Read			Reads the Jedec ID
Read					Reads one byte from the serial flash and returns byte(max of 25 MHz CLK frequency)
Read_Cont				Reads multiple bytes(max of 25 MHz CLK frequency)
HighSpeed_Read			Reads one byte from the serial flash and returns byte(max of 50 MHz CLK frequency)
HighSpeed_Read_Cont		Reads multiple bytes(max of 50 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
Auto_Add_IncA_EBSY		Initial Auto Address Increment process with EBSY
Auto_Add_IncB_EBSY		Successive Auto_Address_Increment process after AAI initiation with EBSY and WRDI/DBSY
Chip_Erase				Erases entire serial flash
Sector_Erase			Erases one sector (4 KB) of the serial flash
Block_Erase_32K			Erases 32 KByte block memory of the serial flash
Block_Erase_64K			Erases 64 KByte block memory 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), 1994-2005	    */
/* Example "C" language Driver of SST25VF040B Serial Flash			*/
/* Conrado Canio, Silicon Storage Technology, Inc.                  */
/*                                                                  */
/* Revision 1.0, November 4th, 2005			  						*/   
/*                                                                  */
/*																	*/
/********************************************************************/

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

/* Function Prototypes */

void init();
void Send_Byte(unsigned char out);
unsigned char Get_Byte();
void Poll_SO();
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();
void EBSY();
void DBSY();
unsigned char Read_ID(ID_addr);
unsigned long Jedec_ID_Read(); 
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 byte1, unsigned char byte2);
void Auto_Add_IncB(unsigned char byte1, unsigned char byte2);
void Auto_Add_IncA_EBSY(unsigned long Dst, unsigned char byte1, unsigned char byte2);
void Auto_Add_IncB_EBSY(unsigned char byte1, unsigned char byte2);
void Chip_Erase();
void Sector_Erase(unsigned long Dst);
void Block_Erase_32K(unsigned long Dst);
void Block_Erase_64K(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: Poll_SO													*/
/*																		*/
/* This procedure polls for the SO line during AAI programming			*/
/* waiting for SO to transition to 1 which will indicate AAI programming*/
/* is completed															*/
/*																		*/
/* Input:																*/
/*		SO																*/
/*																		*/
/* Output:																*/
/*		None															*/
/************************************************************************/
void Poll_SO()
{
	unsigned char temp = 0;
	CE_Low();
	while (temp == 0x00)	/* waste time until not busy */
		temp = SO;
	CE_High();
}

/************************************************************************/
/* 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 */