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I am trying to choose an SPI flash device for my FPGA and I want to verify if I am understanding the terminology correctly. enter image description here

Bitstream is the configuration data code used to implement the logic in the FPGA.

Flash density is the overall size of the Flash.

Sector is the partition in memory that holds the bitstream.

I might be way off but please help me understand the meaning of each.

Thank you

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  • \$\begingroup\$ Bitstream size is the maximum number of bits required by the FPGA. You still have 9 sectors of flash memory available. \$\endgroup\$ Nov 25 at 10:33
  • \$\begingroup\$ How is bitstream size relevant to the sector memory? does flash get sent multiple bitstreams or just one that is divided into its relevant sector? \$\endgroup\$
    – Shannon
    Nov 25 at 10:55
  • \$\begingroup\$ No need to worry about how the flash stores the bitstream. Your FPGA needs to read the configuration bitstream at each boot and the flash memory that is a linear address array of bytes will deliver it. \$\endgroup\$ Nov 25 at 11:20
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"Sector" is the erase block size, so you cannot rewrite a block smaller than that, so you need to align the start of the image to an erase block boundary.

It also seems that an additional sector is required to note down which configuration is active (again, because overwriting that information is possible only by erasing an entire sector).

So, for 1.48 Mbit, which is a bit less than 192kB, you need 3*64k per image, plus one extra, so 7 sectors are used. The smallest available flash is 8 sectors, so one sector is unused. The rightmost two columns should add up to a power of two, because flash sizes will be a power of two.

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You have it correct, except that sector is just a chunk of 65536 bytes of memory, as indicated in yellow by your datasheet.

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