05-05-2009 10:25 PM
I am in schematic/PCB design stage of my application and I need to select two pin compatible Spartan 3A family FPGAs (of different logic densities) for it, so that if my application logic is not fitted into the lower density device, I can just replace it with a higher density device without board re-spin. I have zeroed on two FPGAs - 1. XC3S400A and 2. XC3S700A. The device package is FT256 for both devices.
There are lot of differences in pin configuration of XC3S400A and XC3S700A though the package is same, FT256.
1. There are some pins which is INPUT in XC3S400A but VCC/VREF/GND in XC3S700A.
2. There are some pins which is VREF in XC3S400A but GND in XC3S700A.
3. There are some pins which is I/O in XC3S400A but VCC/VREF/GND in XC3S700A.
Is it possible to migrate from XC3S400A to XC3S700A without changing the footprint/pin traces? And if the answer is yes, then is any guidelines available?