flexibility against clock skew and can eliminate almost all buffer insertion needed to fix hold violations in scan mode.

KEY Setup or hold library values can be negative individually, but their sum must stay positive; negative scan hold eases scan-mode hold fixing.

nxtgrd vs TLUPlus File

• Both nxtgrd and TLUPlus files are generated from the same ITF file using the grdgenxo utility in StarRC, with matching tool versions.
• Both contain similar RC interconnect information and capacitance tables, but their file formats differ.
• The ICC extraction engine (rc_extract) does not accept the format used inside the nxtgrd file, so it cannot consume nxtgrd directly.

KEY nxtgrd and TLUPlus hold similar RC data but in different formats, and ICC's rc_extract cannot read the nxtgrd format.

ICC to StarRC Extraction Correlation

• Ensure the same ITF file is used to generate both the TLUPlus files (used in ICC) and the nxtgrd files (used in StarRC).
• Make sure the nxtgrd and TLUPlus files are generated with the same grdgenxo version.
• Pass the operating temperature to StarRC via OPERATING_TEMPERATURE; ICC picks this up automatically from its operating condition.
• Make sure pin capacitance is provided to StarRC - ICC reads it from the .db files, and StarRC reads it from the .db files in the LM view; if LM views are absent, supply pin capacitance via SKIP_CELL_PORT_PROP_FILE in StarRC.
• Turn off virtual shield extraction with set_extraction_options -virtual_shield_extraction false.
• Keep the metal-fill settings consistent between ICC and StarRC; the recommended approach is to correlate with no metal fill in either tool.