Answers Database
Virtex ngdbuild: ERROR:NgdHelpers:664 - Period specification "TS_clkdv" references the TNM group "clkdv", which contains only pad elements
Record #6402
Product Family: Software
Product Line: FPGA Implementation
Product Part: ngdbuild
Product Version: 2.1i
Problem Title:
Virtex ngdbuild: ERROR:NgdHelpers:664 - Period specification "TS_clkdv" references the TNM
group "clkdv", which contains only pad elements
Problem Description:
Urgency: Standard
Problem Description:
ngdbuild may issue the following error if TNM and PERIOD constraints are used on the
input clock net of the CLKDLL.
ERROR:NgdHelpers:664 - Period specification "TS_clkdv" references the TNM group
"clkdv", which contains only pad elements. Only synchronous elements are
permitted in a period specification. If this group was intended to reference
the synchronous elements driven by the pad(s), you may need to change the TNM
property to a TNM_NET property, so that it will be traced forward from the
pad(s).
Solution 1:
This error is caused by the TNM group only containing PAD elements. When putting
TNM and PERIOD constraints on the input PAD net, they will be pushed through the
CLKDLL element to the individual output. In this case, the CLKDV output drives only
OBUF and off the chip, so the time group only contains an OPAD. Time group with
only PADs in the PERIOD constraint will issue this error.
To workaround this problem, users need to remove the TNM/PERIOD constraints from
the CLKDLL input, and create the appropriate specs at the CLKDLL outputs.
If the output or outputs of the CLKDLL drive the clock pins of the FF, this error will not
occur, because the time group/groups contain clocked elements(FF). It only occurs when the
time group has only PAD elements.
End of Record #6402 - Last Modified: 06/18/99 10:57 |
