Answers Database

FPGA: Default configuration of 2000, 3000, 4000 family IOBs (pullup)


Record #152

Problem Title:
FPGA: Default configuration of 2000, 3000, 4000 family IOBs (pullup)


Problem Description:



Solution 1:




In the XC2000 family, the IOBs should have defined voltages, which can be
accomplished either by connecting an external pullup or an external signal
to it, or by driving the pin with an internal signal. (see p.518, 1991
User Guide and Tutorials)

In the 3000 and 4000 families, if an IOB is unused, it will be configured as an

input with a pullup attached to it.  This may not be immediatedly
obvious within EDITLCA, but if an unused IOB is viewed using the
EDITBLK command, the connection can be seen.




End of Record #152