06-20-2012 08:42 AM
I am currently working towards integrating field firmware updates for a range of designs based on a Spartan3A FPGA configured from an M25P32 PROM.
Digging into the documentation I have noticed that the Spartan3A will always read it's first configuration from address 0 of the PROM and the M25P32s protection bits protect from the highest memory address downwards. This means that we cannot use write protection on the PROM to protect our golden configuration data.
Is anyone aware if there is a way around this, either making the FPGA read it's configuration data from a higher address in the PROM, making the PROM protect from the lowest memory address upwards or alternately a pin for pin replacement PROM that is compatible with Spartan3A FPGAs?
I noticed the other PROM types listed in IMPACT and whilst they allow the protection we require they could not replace the M25P32 PROMs without a board respin. I also noticed that the default setting for the S25FL032P is to protect from the upper memory addresses downwards, does anyone know if this is a standard?
Any input is appreciated, all the better if I'm wrong about anything!