How is the Post-Configuration CRC run time calculated for the Spartan-3A?
The Post-Configuration CRC checking engine continuously runs in the device as long as there is a clock source clocking the CRC logic.
The device shifts out one bit from the configuration logic per clock period; this is shifted into the CRC checking function consisting of a shift register.
You can calculate the total run time for one CRC check by multiplying the total number of configuration bits by the clock period.
- XC3S50A has 437,312 bits running at 12 MHz; will take 0.0364 seconds
- XC3S1400A has 4.755,296 bits running at 12 MHz; will take 0.39627 seconds