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What is the real nRF52840 max writes to a flash block?

The nRF52840 OPS 0.5.1, describes nWRITE,BLOCK as the amount of writes allowed in a block between erases, and lists nWRITE,BLOCK = 403 Maximum.

It looks like 8 blocks are in a 4 kB page, so each block is 512 Bytes.

Does this mean that only 403 of the 512 bytes in a page can be written? Or does the 403 number mean something else?

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  • Ah, the NVMC only supports 32 bit write operations, so it takes 128 write operations to write the entire 512 byte block. That leaves 275 additional writes available to overwrite individual addresses within that block.

    So the entire block can be written without violating the nWRITE, BLOCK spec. And there are enough additional writes to allow the entire block to be overwritten a second time.

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  • Ah, the NVMC only supports 32 bit write operations, so it takes 128 write operations to write the entire 512 byte block. That leaves 275 additional writes available to overwrite individual addresses within that block.

    So the entire block can be written without violating the nWRITE, BLOCK spec. And there are enough additional writes to allow the entire block to be overwritten a second time.

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