sst29xe020.txt

SST 系列Nor flash 的读写源码

Software
Drivers


29EE020 / 29LE020 / 29VE020
2 Megabit Page Mode EEPROM


December 1997




ABOUT THE SOFTWARE
This application note provides software driver examples for 29EE020, 2 Megabit Page Mode EEPROM, 
that can be used in any microprocessor based system. Software driver examples used in this document 
utilize two programming languages: (a) high -level "C" for broad platform support and (b) optimized 8086 
assembly language. In many cases, software driver routines can be inserted "as is" into the main body of 
code being developed by the system software developers. Extensive comments are included in each rou-
tine to describe the function of each routine. The driver in "C" language can be used with many 
microprocessors and microcontrollers, while the 8086 assembly language provides an optimized solution 
for 8086 microprocessors.
NOTE:
The 29EE020 is for 5.0 volt applications, the 29LE020 is for 3.0 volts application, and the 29VE020 is for 
2.7 volt applications. Device functionality is identical for application of this software. For convenience, only 
the 29EE020 will be referenced in the example codes provided.
ABOUT THE 29EE020
Companion product datasheets for the 29EE020 should be reviewed in conjunction with this application 
note for a complete understanding of the device.
The recommended method for writing the 29EE020 employs the JEDEC approved "enable software pro-
tection page write" (SDP) algorithm. Using this method, any write operation (128 bytes) requires the 
inclusion of a series of three byte-load operations, which precede the data loading operation. The three 
byte-load sequence enables the SDP option during page write operation. SDP provides optimal protection 
from inadvertent write cycles, e.g., those triggered by noise during the system power-up or power-down. 
After the initial data byte-load cycle, the host must continue to load a byte into the page buffer within the 
byte-load cycle time (TBLC) of 100 祍 for the 29EE020 to stay in the page load cycle. Additional bytes can 
then be loaded within the same page, in any order. The page load cycle will terminate if no additional byte 
is loaded into the page buffer within 200 祍 (TBLCO) from the last byte-load cycle, i.e. no subsequent 
WE# high-to-low transition after the last rising edge of WE#.


	Both the C and 8086 assembly code in the document contain the following routines, in this order:
	Name	Function
	Check_SST_29EE020	Check manufacturer and device ID
	Write_29EE020	Alter data
	Check_Toggle_Ready	End of write detection using Toggle bit
	Check_Data_Polling	End of write detection using Data# polling
	Enable_Chip_Data_Protection	Enable JEDEC standard software data protection




"C" LANGUAGE DRIVERS

/******************************************************************************************************/
/* Copyright Silicon Storage Technology, Inc. (SST), 1994-1997	                                      */
/* Example "C" language Driver of 29EE020 2 Mbit Page Mode EEPROM	                              */
/* Chi Chung Yin, Silicon Storage Technology	                                                      */
/*	                                                                                              */
/* Revision 2.0, April 8, 1997	                                                                      */
/*	                                                                                              */
/* This file requires these external "timing"  routines:	                                      */
/*	                                                                                              */
/*	1.)  Delay_1_Milli_Second	                                                              */
/*	2.)  Delay_10_Milli_Second	                                                              */
/*	3.)  Delay_10_Micro_Second	                                                              */
/******************************************************************************************************/

#define FALSE			0
#define TRUE			(~FALSE)

#define ROW_SIZE		128		/* Must be 128 bytes for 29EE020  */

#define SST_ID			0xBF		/* SST Manufacturer抯 ID code              */
#define SST_29EE020		0x10		/* SST 29EE020 device code                 */
						/* NOTE-Use "0x12" for 29LE020 and 29VE020 */

typedef unsigned char 		BYTE;

/*____________________________________________________________________*/
/*                       EXERNAL ROUTINES                             */
/*____________________________________________________________________*/

extern void	Delay_1_Milli_Second();
extern void	Delay_10_Milli_Second();
extern void	Delay_10_Micro_Second();
extern void	Check_Toggle_Ready(BYTE far *);
extern void 	Check_Data_Polling(BYTE far *, BYTE);




******************************************************************************************************/
/* PROCEDURE: 	Check_SST_29EE020	                                                             */
/*	                                                                                             */
/* This procedure  decides whether a  physical hardware device has a SST	                     */
/* 29EE020 2 Mbit Page Mode EEPROM installed or not.	                                             */
/* 	                                                                                             */
/*	                                                                                             */
/* Input:	                                                                                     */
/*          None	                                                                             */
/*	                                                                                             */
/* Output:	                                                                                     */
/*  	    return -1:  indicates not a SST 29EE020	                                             */
/*          return 0:   indicates is  a SST 29EE020	                                             */
/*****************************************************************************************************/

int Check_SST_29EE020()
{
	BYTE far  *Temp;
	BYTE SST_id1;
	BYTE SST_id2;
	int    ReturnStatus;

	/*  Issue the Software Product ID code to 29EE020   */  

	Temp  = (BYTE far *)0xC0005555;	         /* set up address to be C000:5555h	*/
	*Temp = 0xAA;	                         /* write data 0xAA to the address	*/
	Temp  = (BYTE far *)0xC0002AAA;	         /* set up address to be C000:2AAAh	*/
	*Temp = 0x55;	                         /* write data 0x55 to the address	*/
	Temp  = (BYTE far *)0xC0005555;	         /* set up address to be C000:5555h	*/
	*Temp = 0x90;	                         /* write data 0x90 to the address	*/

	Delay_10_Milli_Second();

	/* Read the product ID from 29EE020 */

	Temp  = (BYTE far *)0xC0000000;	         /* set up address to be C000:0000h	*/
	SST_id1  =  *Temp;	                 /* get first ID byte	                */
	Temp  =  (BYTE far *)0xC0000001;	 /* set up address to be C000:0001h	*/

	if ((SST_id1 == SST_ID) && (SST_id2 ==SST_29EE020))  
		ReturnStatus = 0;
	else
		ReturnStatus = -1;




/	/* Issue the Soffware Product ID Exit code thus returning the 29EE020	*/
	/* to the read operating mode		                                */

	Temp  = (BYTE far *)0xC0005555;	/* set up address to be C000:5555h	*/
	*Temp = 0xAA;	                /* write data 0xAA to the address	*/
	Temp  = (BYTE far *)0xC0002AAA;	/* set up address to be C000:2AAAh	*/
	*Temp = 0x55;	                /* write data 0x55 to the address	*/
	Temp  = (BYTE far *)0xC0005555;	/* set up address to be C000:5555h	*/
	*Temp =0xF0;	                /* write data 0xF0 to the address	*/

	Delay_10_Milli_Second();

	return(ReturnStatus);
}



/******************************************************************************************************/
/* PROCEDURE: 	Write_29EE020		                                                              */
/*			                                                                              */
/* This procedure can be used to write a total of 128 bytes at one write cycle to the	              */
/* SST抯 29EE020.		                                                                      */
/*			                                                                              */
/* Input:			                                                                      */
/*           SRC     SOURCE address containing the data which will be		                      */
/*                   written into the 29EE020.		                                              */
/*           Dst     DESTINATION address which will be written with the		                      */
/*                   data passed in from ds:si		                                              */
/*			                                                                              */
/* Output:		                                                                              */
/*             None		                                                                      */
/******************************************************************************************************/

void Write_29EE020 (BYTE far *Src,    BYTE far *Dst)
{
             BYTE far *Temp;
             BYTE far *SourceBuf;
             BYTE far *DestBuf;
             int Index;
             
             SourceBuf = Src;
             DestBuf = Dst;