The bitstream keeps loading until the end
of startup (EOS). When MMCM wait or DCI match is enabled before the
DONE startup cycle, padding (all 0
s or all 1s) is required between bitstreams to
compensate for the total wait time. Otherwise, the following bitstream can potentially
overwrite the previous bitstream. The formula for the padding size is cfg_bus_width x total_wait_time / CCLK_period.