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Jcole's avatar
Jcole
Icon for Occasional Contributor rankOccasional Contributor
2 years ago
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Generic Serial Flash Interface addressing only generating 22 bit addressing for 24 bit flash

New to using some of the Avalon based cores. I generated a 128MB Generic Serial Flash Interface core for my EPCQ128A Flash, the addressing is only Avalon memory is section is 22 bits, but how do I se...
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  • FvM's avatar
    FvM
    2 years ago

    128 MBit Flash uses 24-bit-wide byte address. AVMM interface has however 22 DW addresses + 4 byte-enable lines to access the flash. A doubleword access at AVMM is translated by GSFI core to 4 consecutive internal byte accesses.

FvM's avatar
FvM
Icon for Super Contributor rankSuper Contributor
2 years ago
In my math, 128 MB is 4 MW of 32 bit, or 2^22 * 32. Needs exactly 22 address lines.
Jcole's avatar
Jcole
Icon for Occasional Contributor rankOccasional Contributor
2 years ago

Your math is correct, but I'm slightly confused. If I'm not mistaken, the difference due to the word sizes of the GSFI being 32 bit as compared to the byte addressing of the flash.