AR# 10267: 3.1i XST - ERROR:NgdBuild:393 - Could not find INST(S) 'instance_name' in design 'top_level'.
3.1i XST - ERROR:NgdBuild:393 - Could not find INST(S) 'instance_name' in design 'top_level'.
Keywords: XST, Verilog, hierarchy, 393, NGDBuild
General Description: I encounter the following error:
ERROR:NgdBuild:393 - Could not find INST(S) 'instance_name' in design 'top_level'.
This error appears when:
1. Passing attributes in HDL with the hierarchy switch on. (XST will not write the appropriate hierarchical name in the NCF.)
2. Passing attributes in HDL with the incremental synthesis switch on. XST writes out only one NCF file. (When multiple EDIF files are being read in to the implementation tools, there needs to be an NCF file for every EDIF file if constraints are being passed.)
NOTE: This problem is fixed in the 4.1i software release.
Modify the NCF by adding the hierarchical name. The appropriate hierarchical name will exclude the top level, starting with the second hierarchy. For example:
hierarchy1 instance2 instance3
"Hierarchy1" is the component/module name of the top-level file. "Instance2" represents a component/module in the second level of hierarchy. "Instance3" represents a component/module in the third level of hierarchy.
XST will write out an NCF file similar to the following:
INST fdc_instance IOB="TRUE"
where fdc_instance may reside in "instance3." Therefore, the NCF will need to be modified as follows:
INST instance2/instance3/fdc_instance IOB="TRUE"
Synthesize each HDL file that has constraints separately. XST will write out the corresponding NCF.
Then synthesize the top level file. XST will not re-synthesize the lower level files that have already been synthesized.