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While trying to interface flash SST25VF512 with AT80c51, i find difficulty in Byte program mode of writing to flash.
This is the code i used, could somebody who has worked on this please help me out,
void main(void){ ce = 1; SCK = 0; TMOD = 0x20; TH1 = -3; // 9600 baud SCON = 0x50; TR1 = 1; TI = 1; addr = 0x00000012; Rd_ID = Read_ID(); Byte_Program(addr); void Byte_Program(unsigned long addr){ ce = 0; E_WRSR(); WREN(); Send_Byte(0x02); // Byte Program CMD Send_Byte(((addr & 0xFFFFFF) >> 16)); // sending 3 address bytes Send_Byte(((addr & 0xFFFF) >> 8)); Send_Byte(addr & 0xFF); Send_Byte(0x10); //send data SR_byte = Read_Status_Register(); while((SR_byte &0x01) != 0x00){ SR_byte = Read_Status_Register(); } ce = 1; } void E_WRSR(){ ce = 0; Send_Byte(0x50); // enable Status Reg ce = 1; ce = 0; Send_Byte(0x01); // select write to status register Send_Byte(0x00); // mode 0, ce = 1; } void WREN(){ ce = 0; Send_Byte(0x06);// to Write enable ce = 1; } unsigned char Get_Byte(){ unsigned char i=0, in=0, temp=0; for(i=0;i<8;i++){ in = (in << 1); temp = SO; SCK = 1; if (temp == 1){ in = in | 0x01; } SCK = 0; } return in; } void Send_Byte(unsigned char b_out){ for(i=0;i<8;i++){ if((b_out & 0x80) == 0x80) si = 1; else si = 0; SCK = 1; b_out = (b_out << 1); SCK = 0; } }
Thanks in advance,
You probably do not want to write the status register before every write operation. Yes, there is a write enable bit there, and yes, this sequence will work correctly. However, the status register in these types of flash is non-volatile, implemented with the same flash technology as the rest of the chip. Every time you write the status register, you effectively erase it and reprogram it. After the rated number of cycles on your flash chip, the status register will burn out and the chip will stop working, even if the data sectors are still good.
The WREN command is sufficient to tell the chip to allow programming. It does not cause the status register to be erased and reprogrammed as does WRSR. Using WRSR is not necessary, and will limit the lifetime of the chip if you frequently write data.
Thanks Dave, so you suggest WRSR need not be written IN the write operation is it, fine, then how do we set the memory protection bits? Without setting them, is there any way to write,
"After the rated number of cycles on your flash chip, the status register will burn out and the chip will stop working, even if the data sectors are still good." Could you please tell this rated number of cycles. Can write operation process be completed within that?
"Using WRSR is not necessary, and will limit the lifetime of the chip if you frequently write data." Is it apart from the 10,000 cycles for the chip as a whole?
Then how do we get to write data and check also that the program is running fine,
waiting for reply,
sorry drew,
"Could you please tell this rated number of cycles."
That'll be in the datasheet
Note that it is not a precise number below which everything is fine and above which nothing works; the thing wears out gradually.
Thanks Neil, How do you say the write function code should be, After writing the byte, the status reg reads 02, ie finished writing. Then should there be some change in the read function code? Where do you think is the mistake,
"However, the status register in these types of flash is non-volatile, implemented with the same flash technology as the rest of the chip." How is that only status reg is non volatile? I could nt find this info in datasheet. Where do we get such finer details?
"How do you say the write function code should be"
Never mind what I say - what does the Manufacturer say?
Don't SST provide example code for this?
If that had worked, would not have asked you
Had followed the manufacturer's code supposedly there are fine changes to be done thought you got an eye for detail SST does provide code, though there are things to be added to it like Enable operation etc..