Trace clock tree

updateStatus -force designIsPlaced selectInst * dbSet selected.pStatus placed setCTSMode -engine ck cleanupSpecifyClockTree specifyClockTree -file /proj/$project_name/work/user/$design_name/$script_path/${design_name}.seperated.trace.ctstch ckSynthesis -check -forceReconvergent -trace /proj/$project_name/work/user/$design_name/$script_path/${design_name}.seperated.trace  

Configure STA environment

What’s STA environment? Specifying Clocks. Clock uncertainty and Clock latency Generated clocks Input paths constraint Output paths constraint  Timing path groups External attributes modeling  Check design rules Refine timing analysis Point-to-point specification Set up environment for static timing analysis. Specification of correct constraints is important in analyzing STA results. Design environment should be specified accurately… read more »

Path delay in cross clock domain

Sometimes, for cross clock domain timing analysis, incorrect timing report from mistake Path Delay due to big source clock paths latency/skew or target paths latency/skew would lead tool report and fix timing violation wrongly. Designer analysis launch clock paths latency/skew and capture clock paths latency/skew, find out which path(s) is/are too long, for example, it… read more »

Clock Tree Latency Skew Uncertainty

Clock to a SoC/chip is like blood to a dog body. If you want the pet smart and strong, hematological system would be healthy. Just the way blood flows to each and every part of the body and regulates metabolism, clock reaches each and every sequential device and controls the digital events inside the chip…. read more »

CTS Spec UnsyncPin RootPin based on Constraint and Netlist

Turbodebug check Design netlist about clock timing path: Fig. 1 Design/inst_adrctl_slice_bist_ddl/inst_ddl_fdbk_clk_mux #Constraint create_clock -name clk_ddl_test_fdbk [get_pin inst_adrctl_slice_bist_ddl/inst_ddl_fdbk_clk_mux/inst_mux_nand2/hic_dnt_nand2/$NEG_OUTPUT ] -period $PHY_DDL_SCALED_CLK_PERIOD -waveform “0 $PHY_DDL_SCALED_HALF” #CTS Spec file #Excluded Output pin due to create_clock inst_adrctl_slice_bist_ddl/inst_ddl_fdbk_clk_mux/inst_mux_nand2/hic_dnt_nand2/ZN GlobalUnsyncPin +inst_adrctl_slice_bist_ddl/inst_ddl_fdbk_clk_mux/inst_mux_nand0/hic_dnt_nand2/A1 +inst_adrctl_slice_bist_ddl/inst_ddl_fdbk_clk_mux/inst_mux_nand1/hic_dnt_nand2/A1 #—————————————————- # Clock Name : clk_ddl_test_fdbk #—————————————————- AutoCTSRootPin inst_adrctl_slice_bist_ddl/inst_ddl_fdbk_clk_mux/inst_mux_nand2/hic_dnt_nand2/ZN  

Clock divider and CTS

Turbodebug check Design netlist about clk div timing path: Fig. 1 Design/inst_clk_div Fig. 2, 3 Design/inst_clk_div/inst_clk_div_mux/inst_mux_nand2/hic_dnt_nand2/ZN Fig. 4 Design/inst_clk_div/inst_clk_div_dff/hic_dnt_out_reg/Q (constraint below create_generated_clock set it as RootPin, but design inst_clk_div/inst_clk_div_mux/inst_mux_nand2/hic_dnt_nand2/ZN as RootPin in CTS Spec file, as Fig. 4 Q pin (out_p) connects to Fig. 2 in0 actually) #Constraint create_clock [get_ports clk4x ] -name dummy_clk4x -period 0.5*0.833 -waveform… read more »

design flow simple

Simplify a general design flow post-floorplan should be: 1st timing driven placement according to constraints, skew/latency was considered as ‘ideal’ zero, optDesign –preCTS. 2nd CTS, optDesign –postCTS. Clock tree have insertion or propagation delay after CTS. 3rd routing, optDesign –postRoute, optDesign –hold -postRoute. Usually, fix setup violation first, then hold violation in order to obtain… read more »

Clock Tree Synthesis

In clock tree synthesis, do ONE thing only, insert CLK INV (NOT CKBUFF !) which could fix rising and falling transition/duty, to min clock tree latency and skew, balance sink/leaf pins which should be balanced, don’t balance pins which should not be balanced. CTS Macro Model Let tool know the segment of clock path latency which… read more »

Prepare files and check netlist

1. Which library files do backend engineers need? Timing: lib RC delay: capTable, QRC tech, QRC lib Physical: lef, gds Route rule: tech lef, tech file Xtalk: cdb Power: VoltageStorm tech, VoltageStorm lib 2. Which files are about design? Netlist, constraint, IO file, scan def 3. What should be checked before APR? Check library files,… read more »