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AR# 5608

Virtex/-E/-II/-II Pro/-4/-5 - What happens when VCCO, VCCINT, or VCCAUX is lost during device operation?


What happens when VCCO, VCCINT, or VCCAUX is lost during device operation?


The following describes what happens when VCCO, VCCINT, or VCCAUX is lost during device operation. The loss of power will not damage the device.

When VCCINT is lost in a Virtex/-E/-II/-II Pro/-4/-5 device:

If the VCCINT (core voltage) is lost at any time, the device configuration data will also be lost. This means that when power is restored to VCCINT, reconfiguration is necessary. The output pins are put into a 3-state condition for as long as the VCCINT power is down. When power is restored, they will revert to the mode-pin configuration (either pulled High or in 3-state).

When VCCAUX is lost in the Virtex-II/-II Pro/-4/-5 device:

If VCCAUX is lost, the behavior is similar to when VCCINT is lost. The POR circuit recognizes loss of VCCAUX, and the device shuts down (all memory is cleared, all I/Os are 3-stated, and it then waits for power to return to normal).

Once power returns to normal, the device needs to be reconfigured, just as if power has been applied for the first time.

When VCCO is lost in a Virtex/-E device:

If VCCO is lost during configuration, the output-High signals will be put into a 3-state condition. However, because output-Low signals are not VCCO-dependent, they will still be operational.

When VCCO is lost in a Virtex-II/Virtex-II Pro/Virtex-4 device:

If VCCO is lost during configuration, the output data will be lost. The clamp diode on the I/O might be forward-biased and might draw current. This will not damage the device. If you are considering hot-swapping Virtex-II/-II Pro/-4/-5 devices, see (Xilinx XAPP251): "Hot-Swapping Virtex-II Devices" for more information:


(NOTE: The VCCO for the configuration banks are connected to a power on reset (POR) circuitry. Therefore, if the VCCO for these banks is lost, the device will reset and configuration data will be lost. The outputs will revert to the pre-configuration state.)

The configuration bank for Virtex/-E devices is Bank 2.

The configuration bank for Virtex-II/-II Pro devices is Bank 4.

The configuration bank for Virtex-4 devices is Bank 0.

Additional references:

- For more information on the Virtex/-E configuration sequence, see the Virtex/-E Data Sheet and the (Xilinx XAPP138): "Virtex FPGA Series Configuration and Readback."


- For more information on the Virtex-II/-II Pro configuration sequence, see the Virtex-II/-II Pro/4/5 Data Sheet , Virtex-II/II Pro User Guide (Chapter 3, "Configuration"), and Virtex-4/5 Configuration Guide:

Virtex-II Pro:






AR# 5608
Date Created 08/21/2007
Last Updated 12/15/2012
Status Active
Type General Article