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AR# 14879

5.1i XPower - "WARNING:Power:91 - Can't change frequency of net GLOBAL_LOGIC0_92 to 110.00Mhz"

Description

Keywords: 5.1i, 4.1i, 4.2i, XPower, global_logic0, frequency, Warning, power, 91

Urgency: Standard

General Description:
When I attempt to run XPower on a design, the following warnings are reported:

"xpwr design.ncd design.pcf -o design.pwr

WARNING:Power:91 - Can't change frequency of net GLOBAL_LOGIC0_92 to 110.00Mhz.
WARNING:Power:91 - Can't change frequency of net GLOBAL_LOGIC0_92 to 100.00Mhz.
WARNING:Power:91 - Can't change frequency of net GLOBAL_LOGIC0_92 to 100.00Mhz."

Solution

1

One possibility is that a GND or VCC is tied to the input of a BUFGMUX. XPower assumes that this is a clock signal and attempts to toggle it.

To work around this problem, remove the GND or VCC attached to the input of the BUFGMUX. This can be done at the design level or in FPGA Editor. Once this has been done, you may run the design through XPower.

This problem is fixed in the latest 5.1i Service Pack, available at:
http://support.xilinx.com/support/techsup/sw_updates
The first service pack containing the fix is 5.1i Service Pack 1.

2

If the frequency of an IBUF output is manually assigned, attempts to change the input to the IBUF component result in a warning similar to the following:

"WARNING:Power:91 - Can't change frequency of net reset to 1000.00Mhz."

To work around this, simply do not edit the output of the IBUF first; instead, edit the input of the IBUF first.

This will be fixed in a future software release.
AR# 14879
Date Created 06/14/2002
Last Updated 04/05/2006
Status Archive
Type General Article