AR# 453: SYN2XNF: Use of -s option causes creation of EXT records, XNFPREP Error 3527
SYN2XNF: Use of -s option causes creation of EXT records, XNFPREP Error 3527
Syn2xnf -s creates external "EXT" records causing XNFPREP to fail. Syn2xnf -s (sub) is supposed to create a hierarchical block (without any IOs) but it still creates EXT records for .sxnf file written by Synopsys FPGA Compiler. The XNF format .xnf and .xff files have EXT records. This will cause XNFPREP to give errors related to pads connected to internal nodes.
The cause of the problem is that SYN2XNF -s only works on EDIF format file (which implies Design Compiler). If the design is written out as a .sxnf file, there will still be EXT records written into it. The only solution is to manually remove the EXT records at the end of the .sxnf files generated by Synopsys; or write out an edif format file instead.