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AR# 152

FPGA Hardware - Default configuration of XC2000, XC3000, XC4000 family unused IOBs (pullup)

Description

What is the default configuration of XC2000, XC3000, and XC4000 I/O's?

Solution

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 XC3000 and XC4000 families, if an IOB is unused, it will be configured as an input with a pullup attached to it. This might not be immediately obvious within EDITLCA, but if an unused IOB is viewed using the EDITBLK command, the connection can be seen.

AR# 152
Date Created 08/21/2007
Last Updated 12/15/2012
Status Active
Type General Article