Per the documentation the XEM7310 I/Os should NOT be pulled up during configuration :
“This behavior is controlled by the PUDC_B pin. By default the XEM7310 holds the PUDC_B pin high with a 1kΩ resistor at R26, disabling the weak pull-up on all I/O pins at power on.”
but it seems that they are. Replacing R26 with a lower value (100 ohms, 0 ohms) does not help.
Does anyone know why the XEM7310 I/Os are pulled up during configuration?
Does anyone know how to prevent them from being pulled up during configuration?
Oops, please disregard. This was actually a glitch or power distribution problem with the I/O buffering and over-voltage/under-voltage/ESD protection on the carrier board that I was mounting the XEM7310 on. So while the IOs on the carrier went high whenever the power was cycled or whenever the FPGA on the XEM7310 was configured (even without cycling the power), it was not actually caused by the XEM7310 itself pulling the IOs up during configuration. The existing 1k R26 value appears to work fine to prevent the XEM7310 IOs from being pulled up during configuraiton.