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NAND memory read errors

Question asked by Rygel.Troy1818 on Jan 11, 2014
Latest reply on Jan 13, 2014 by Clive One
Hello,
I will try with this forum as a last resort for my problem, namely getting my NAND memory to play with me.

http://www.ic-on-line.cn/download.php?id=1915099&pdfid=5E619D21E0C125A4A94BC1A860068896&file=0459\h27ubg8t2btr-bc_6373736.pdf

I don't have any experience with NAND before. I am using stm32f407VG with FSMC to communicate with the chip (168Mhz internal clk). My problem is reading the data on the NAND after i have programmed it.

The thing is that sometimes (approx. 0.2%) I get unexpected value. Usually it is only one bit that is wrong (0x30 instead of 0x20, 0x38 instead of 0x8, A6 instead of A2 etc.). The 0.2% is not spread out at random. The first page (8192 bytes) is correct all the time when reading. I have seem a pattern though. It seems that I get no read errors at page 0, some errors on page 1, even more errors in 2 and so on.

Also when I study one of these read errors I can see that about 50% of the time I get the correct value from the NAND memory (verified with oscilloscope). This also seems to be the case for all these problematic addresses.

These are my thoughts:
* I have tried with different blocks but I get the same problems (surely they cannot all be bad blocks??).
* I have tried with a second board with same exact problem.
* I have double and triple checked the pins/connection.
* I know that FSMC works since I can use it for other peripherals with good result (but with another bank)
* I understand the relevancy of the timing for the NAND memory and I suspected something wrong with this a long time but concluded that this is not likely my problem.
* On the same FSMC bus I have another peripheral connected (ssd1963). I have the CS for this chip always high so there should not be any problems I think? This chip is not even initialized (since I would need FSMC with other setting/bank for this).
* I am not using ECC since my board does not need to be very serious project. I just want to play around a little with NAND.

Some code:

  p.FSMC_SetupTime = 0x1;
  p.FSMC_WaitSetupTime = 0x2;
  p.FSMC_HoldSetupTime = 0xA;
  p.FSMC_HiZSetupTime = 0x1;
  FSMC_NANDInitStructure.FSMC_CommonSpaceTimingStruct = &p;
  FSMC_NANDInitStructure.FSMC_AttributeSpaceTimingStruct = &p;
  FSMC_NANDInitStructure.FSMC_Bank = FSMC_Bank2_NAND;
  FSMC_NANDInitStructure.FSMC_Waitfeature = FSMC_Waitfeature_Enable;
  FSMC_NANDInitStructure.FSMC_MemoryDataWidth = FSMC_MemoryDataWidth_8b;
  FSMC_NANDInitStructure.FSMC_ECC = FSMC_ECC_Disable;
  FSMC_NANDInit(&FSMC_NANDInitStructure);
  FSMC_NANDCmd(FSMC_Bank2_NAND, ENABLE);

#define NAND_BASE 0x70000000
#define CMD_AREA (u32)(1<<16)
#define ADDR_AREA (u32)(1<<17)
#define DATA_AREA (u32)(0)
#define NAND_CMD (*((volatile uint8_t *)(NAND_BASE | CMD_AREA )))
#define NAND_ADDR (*((volatile uint8_t *)(NAND_BASE | ADDR_AREA )))
#define NAND_DATA (*((volatile uint8_t *)(NAND_BASE | DATA_AREA )))


void hynix_read_byte_cmd(uint_32 address)
{
  uint_16 column = 0;
  uint_16 page = 0;
  uint_16 block = 0;
  uint_16 plane = 0;

  column = address & 0x1FFF; // 13 bits (don't care about the 14:th bit for ECC memory)
  page = (address >> 13) & 0xFF; // 8 bits
  block = (address >> (13 + 8)) & 0x3FF; // 10 bits
  plane = (address >> (13 + 8 + 10)) & 0x1;

  NAND_CMD = 0x00;

  NAND_ADDR = (column >> 0) & 0xFF;
  NAND_ADDR = (column >> 8) & 0x1F;
  NAND_ADDR = page;
  NAND_ADDR = ((block << 1) & 0xFE) | plane;
  NAND_ADDR = (block >> 7);

  NAND_CMD = 0x30;
}


uchar hynix_read_byte()
{
  return NAND_DATA;
}


I cant get my head around this problem. Perhaps someone with experience from NAND memories can give me some pointers on things that I need to consider.

Regards,
/rygelxvi

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