Synopsys Timing Constraints And Optimization User Guide 2021 //top\\ 🆕 Trusted

Essential for clock dividers or PLL outputs. It ensures the tool understands the phase relationship between the master clock and its derivatives.

# Relax setup check to 3 clock cycles set_multicycle_path 3 -setup -from [get_pins reg_a/CP] -to [get_pins reg_b/D] # Adjust hold check accordingly (usually N-1 cycles) set_multicycle_path 2 -hold -from [get_pins reg_a/CP] -to [get_pins reg_b/D] Use code with caution. Asynchronous Clock Groups ( set_clock_groups )

Properly defining virtual clocks for input/output delay constraints to ensure accurate interface timing. B. Input and Output Delays

When the design moves to physical implementation and signoff with , the timing constraints continue to guide the process. Engineers use PrimeTime, Synopsys' golden signoff-quality STA tool, to run the final, accurate timing checks before tapeout. It reads the design, parasitic information (like SPEF files), and the SDC constraints to ensure every timing path meets its requirements. synopsys timing constraints and optimization user guide 2021

At the heart of the guide is the format. SDC is the industry-standard language used to describe the timing, power, and area constraints of a design.

Synopsys tools prioritize Design Rule Violations over performance targets. If your design has major Max Transition or Max Capacitance violations, the tool will focus on fixing those first, often degrading timing. Always ensure your environment specifies realistic electrical constraints:

Specifying when data arrives at a port relative to a clock edge. Essential for clock dividers or PLL outputs

Once a design is physically implemented, a final, accurate timing analysis must be performed before tape-out.

Mastering the Clock: A Deep Dive into the Synopsys Timing Constraints and Optimization User Guide

Startpoint: reg_a (rising edge-triggered flip-flop clocked by SYS_CLK) Endpoint: reg_b (rising edge-triggered flip-flop clocked by SYS_CLK) Path Group: SYS_CLK Path Type: max (Setup check) Point Incr Path ----------------------------------------------------------- clock SYS_CLK (rising edge) 0.00 0.00 clock network delay (ideal) 0.00 0.00 reg_a/CP (gtech_fd2) 0.00 0.00 r reg_a/Q (gtech_fd2) 0.12 0.12 f u_logic/U1/Y (bufx2) 0.45 0.57 f u_logic/U2/Y (nand3x1) 0.88 1.45 r reg_b/D (gtech_fd2) 0.01 1.46 r Data Arrival Time 1.46 clock SYS_CLK (rising edge) 2.00 2.00 clock network delay (ideal) 0.00 2.00 clock uncertainty -0.15 1.85 reg_b/CP (gtech_fd2) 0.00 1.85 r library setup time -0.08 1.77 Data Required Time 1.77 ----------------------------------------------------------- Slack (MET) 0.31 Use code with caution. How to Fix Timing Violations often degrading timing.

The guide concludes with a "Best Practices" section, highlighting common errors:

set_max_transition 0.25 [current_design] set_max_capacitance 0.5 [current_design] set_max_fanout 20 [current_design] Use code with caution. 7. Analyzing Timing and Troubleshooting Violations