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12435 Discussions

Parallel Flash Loader -- Selecting from Multiple Images at Power-On

Honored Contributor II

I'm currently booting an FPGA from external flash via a CPLD with a PFL megafunction instantiated.. 


I'd like to have 2 images on the flash, and based on the state of an input select pin at power on, the PFL will decide which sector contains the image to load. 


The problem I'm having is that the option bits containing the start sector is in flash, therefore it'll always load from the same sector offset. 


Alternatively, outside of the PFL I can set an upper address line high and thereby trick the PFL to load an image that is at a different address, but this didn't work either, for reasons unknown. I suspect, that it may have to do with the CFI table.. the PFL may first be reading the CFI table before doing anything, and since I've created an offset, it won't be found. 


I can't imagine selecting between multiple images from the flash at runtime is a new concept.. so what am I missing?
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