AR# 3026


CPLD XC9500/XL/XV Family - When can I use internal pull-up resistors?


When are the internal pull-ups in the IOB active, and when can I program them?


The IOB of every XC9500 family device has a pull-up resistor attached to each I/O pin to prevent the pins from floating when the device is not in normal operation.

The resistor becomes active during device programming and system power-up. The resistor is also activated for an erased device. This includes both new devices and devices that have been programmed, then erased.

At all other times, the resistor is deactivated unless the user has specific the termination as pull up in the FIT properties box, this will then be enabled for all inputs and Bi-Directional pins.

There is also a weak "Bus Hold" Present on the additional information can be found in the CPLD I/O User Guide under the "Half Latch" section.

For other common CPLD questions, please see the CPLD FAQ: (Xilinx Answer 24167).

AR# 3026
Date 12/15/2012
Status Active
Type General Article
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