For complex SoCs, Synopsys highlights the Timing Constraints Manager (TCM) , which automates the verification and promotion of constraints from IP to SoC levels.
. While the exact chapter numbering can vary slightly between tool releases (e.g., version R-2020.09 vs. S-2021.06), the core content structure remains consistent.
: Ensures data remains stable long enough after the clock edge to prevent corruption. Violations are fixed by inserting buffers. 2. Defining the Clock Network synopsys timing constraints and optimization user guide 2021
# Prioritize timing over area considerations during compile set_max_area 0 # Fix hold time violations automatically during synthesis (compile_ultra) set_fix_hold [all_clocks] # Enable high-effort optimization for aggressive timing closure compile_ultra -retime -gate_clock Use code with caution.
: Instructions for create_clock and create_generated_clock to identify primary oscillators and internal clock dividers. For complex SoCs, Synopsys highlights the Timing Constraints
The 2021 guidelines emphasize that constraints should be . Over-constraining forces the tool to work unnecessarily hard, leading to bloated area and excessive power consumption. Under-constraining, conversely, leads to optimistic results that fail in silicon. 2. Defining the Clock Tree
The guide introduces a "Board-Aware" constraint flow. S-2021
# Constrain an input port relative to an external clock set_input_delay -max 3.5 -clock SYS_CLK [get_ports data_in] set_input_delay -min 1.0 -clock SYS_CLK [get_ports data_in] # Constrain an output port relative to an external clock set_output_delay -max 4.0 -clock SYS_CLK [get_ports data_out] set_output_delay -min 0.5 -clock SYS_CLK [get_ports data_out] Use code with caution. Environmental Attributes
to make critical trade-offs between timing, area, and power. Workflow Integration
Buried in Chapter 6 ("Optimizing for High Speed") is a warning that saves countless ECO cycles: