UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 22409

9.1i NGDBuild/Constraint - Offset constraints with OFFSET OUT BEFORE and OFFSET IN AFTER cause "ERROR:XdmHelpers:667."

Description

When I use "OFFSET OUT BEFORE" constraint for the time group, which contains one or more pad elements similar to the following:

NET <net1> TNM_NET = net1_GRP;

NET <net2> TNM_NET = net2_GRP;

TIMEGRP net_GRP = net1_GRP net2_GRP;

OFFSET = OUT 4.0ns BEFORE <clock> TIMEGRP net_GRP;

The following errors are incorrectly shown in NGDBuild:

"ERROR:XdmHelpers:667 - OFFSET specification "OFFSET=OUT <n> pS BEFORE <clock signal> TIMEGRP <Group>" references a register group <Group>, which contains one or more pad elements. The optional register group must contain only synchronous elements."

Solution

OFFSETs allow the user to specify external data and clock relationships for the timing on paths to and from the I/Os.

1. If <Group> is Clock Register Time Group, the syntax of "OFFSET OUT BEFORE" and "OFFSET IN AFTER" is:

OFFSET OUT BEFORE:

OFFSET = OUT <n> pS BEFORE <clock signal> TIMEGRP <Group>;

OFFSET IN AFTER:

OFFSET = IN <n> pS AFTER <clock signal> TIMEGRP <Group>;

2. If <Group> is Data Path Group, the syntax of "OFFSET OUT BEFORE" and "OFFSET IN AFTER" is:

OFFSET OUT BEFORE:

TIMEGRP <Group> OFFSET = OUT <n> pS BEFORE <clock signal>;

OFFSET IN AFTER:

TIMEGRP <Group> OFFSET = IN <n> pS AFTER <clock signal>;

If EXCEPT is used in Offset constraints which cause the same error, please refer to (Xilinx Answer 20959).

AR# 22409
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article