Cyclone V: switching between application images using altremote_update

I'd first just try reading the image from the epcq.

This is really easy to do if you have access to actual epcq pins.

You just big-bang out a read command (initially test with address 0) and then bit-band in the read data.

For cyclone V (Arria II and later) the epcq is configured for two extra dummy clocks so that they can use epcq256 with 4 byte addresses.

You can read the nv status register to find this out - but for a specific board you know what is there.