Configuration Persist i s required in Tandem PROM configuration for UltraScale devices. Dual purpose I/O used for stage 1 and stage 2 configuration cannot be re-purposed as user I/O after stage 2 configuration is complete. Because of this, the configuration flash cannot be accessed by the user design after Tandem PROM configuration completes. Tandem PCIe should be used if configuration flash update from the FPGA user design is required.
If the CONFIG_MODE option is set correctly for the needed configuration mode, but necessary dual-mode I/O pins are still occupied by user I/O, the following error is issued for each instance during write_bitstream:
ERROR: [Designutils 12-1767] Cannot add persist programming for site IOB_X0Y151.
ERROR: [Designutils 12-1767] Cannot add persist programming for site IOB_X0Y152.
The user I/O occupying these sites must be relocated to use Tandem PROM.