Some Spartan-3A/3AN/3A DSP devices are dual marked with the Speed Grade/Temperature Range of "5C / 4I." Does this mean that all "4I" parts can be used as "5C"?
The 5C and 4I Speed Grade/Temperature Range part combinations can be dual marked as 5C/4I in some Spartan devices. Devices with the dual mark can be used as either -5C or -4I devices.
All Spartan devices with a single mark are guaranteed only for the marked speed grade and temperature range on that part. It is not generally true that "4I" is a replacement for "5C."
For temperature range and speed grade information, please see the device data sheets on www.xilinx.com.