What is the purpose of WP pin in a SPI NOR flash.

• What is the purpose of WP pin in a SPI NOR flash.
  Posted by madhu.wesly01 on 17 Oct, 2017 17:38
• Hi,
  
  I am going to use a SPI NOR flash as a Data logger in my design for storing GPS coordinates. I could not get clarity on the Write Protect(WP) pin on a NOR flash memory. Could any-one let me know what exactly it is and its hardware connections if we want to interface it to a Micro-controller?
  
  Thanks & regards,
  Madhuwesly.
• #1 Reply
  Posted by ataradov on 17 Oct, 2017 18:14
• If you don't need write protection, then just pull-up or pull-down it as described in the datasheet for the device.
• #2 Reply
  Posted by rstofer on 17 Oct, 2017 18:15
• It's probably covered in the datasheet.  It is for the Cypress part but it doesn't do what I though it would do.
  
  http://www.mouser.com/ProductDetail/Carling-Technologies/2GG51-73/
  
  You MAY find that it is pulled high internally and can be ignored.  Or not...
  
• #3 Reply
  Posted by madhu.wesly01 on 18 Oct, 2017 05:17
• Thanks for the reply @ataradov. Could you please let me know what it actually do? Basically, when I have gone through few reference schematics the WP pin is pulled high in the applications.
  My requirements are : READ and WRITE, if possible ERASE/RESET.
• #4 Reply
  Posted by ataradov on 18 Oct, 2017 05:18
• If this pin is low, then flash will disregard any destructive operations (erase/write). Just pull it high and forget about it.
  
  You still have not told us what chip you are using, so here is a quote from some random Micron datasheet:
  

  Quote

  Write protect: The W# input signal is used to freeze the size of the area of memory
  that is protected against program or erase commands as specified by the values in
  BP2, BP1, and BP0 bits of the Status Register.

  Reads pretty clear to me.
• #5 Reply
  Posted by madhu.wesly01 on 18 Oct, 2017 05:25
• Thanks for the prompt reply @ataradov.
  Will the operations - "Erase and Write" considered as disruptive operations when it is active(Active LOW)? In this state can we read from the device?
  Could you please tell me what are the operations can be performed when it is active and inactive?
  
  Thanks & regards,
  Madhuwesly.
• #6 Reply
  Posted by ataradov on 18 Oct, 2017 05:26
• Can you actually tell what device you are using? This is kind of important.
• #7 Reply
  Posted by madhu.wesly01 on 18 Oct, 2017 05:32
• I am using Winbond's SPI NOR Flash - W25Q256FV. And Controller - ATSAMD21G18.
• #8 Reply
  Posted by ataradov on 18 Oct, 2017 05:36
• Well, it says it right in the datasheet "The Write Protect (/WP) pin can be used to prevent the Status Register from being written." That's all it does. The consequences of that you can figure out by reading the description of the Status Register.
  
  Just pull it high, and forget about it, you will be able to do whatever with the flash.