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Hot!NOT ABLE TO WRITE TO STATUS REGISTER OF SST25VF040B spi flash

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san123
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2020/12/31 02:37:56 (permalink)
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NOT ABLE TO WRITE TO STATUS REGISTER OF SST25VF040B spi flash

Hello All,
I am testing SST25VF040B serial flash ic using DIOs available on NI PXIe 6366 card in labview.
I have provided CLK, CE, and SI signals through DIOs in labview. Clock used for 6.25MHz.
The WP(write protect) and HOLD pins are connected to Vcc(3.3v). As the NI card is 5V TLL, I have used level translator ics at each input signal(CLK, CE and SI).
I have to write data using AAI programming and for that first I need to unprotect the flash memory. So first I am writing to status register to unprotect the memory using WRSR command as per the timing diagram given in the datasheet. But status register shows default value when read after writing to status register. I am not able to figure out why it is not writing to status register. Please suggests some direction to debug this problem.
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    cirilo.b
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    Re: NOT ABLE TO WRITE TO STATUS REGISTER OF SST25VF040B spi flash 2020/12/31 15:04:59 (permalink)
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    The only bits I see that can be written in the SR are the BPL, BPn bits. Some care is required when altering these bits.  For example BPL can be written regardless of the state of #WP, but the BPn bits can only be consistently written if #WP is high; if #WP is low then BPL determines whether or not you can write the BPn bits.  Keep in mind that the #WP is part of a failsafe mechanism and that you still need to execute the WREN instruction.  As per the datasheet:
     
    Prior to executing any Byte Program, Auto Address Increment (AAI) programming, Sector Erase, Block Erase, Write STATUS Register, or Chip Erase instructions, the Write Enable (WREN) instruction must be executed first.
     
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    san123
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    Re: NOT ABLE TO WRITE TO STATUS REGISTER OF SST25VF040B spi flash 2021/01/03 23:58:57 (permalink)
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    Yes, I am taking care of all these requirements. Kept #WP is high and executing the WREN instruction before executing Write STATUS Register instruction. But still, STATUS Register is showing default value (not the one I am trying to write) when read immediately after executing WREN and Write STATUS Register instructions.
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