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  

Check clock gating

Figure 1  A clock gating check A clock gating check occurs when a gating signal can control the path of a clock signal at a logic cell. An example is shown in Figure 1. The pin of logic cell connected to clock is called clock pin and pin where gating signal is connected to is gating pin. Logic… read more »

Crosstalk delay on timing verificaiton

Figure 1  Crosstalk in data and clock paths 1.  Setup analysis Launch clock path sees positive crosstalk delay so that data is launched late. Data path sees positive crosstalk delay so that it takes longer for data to reach destination (D pin in capture FF). Capture clock path sees negative crosstalk delay so that data… read more »

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 »

same source create_generated_clock -add

#Constraint set CLK_PHASE_0_SRC “dummy_clk4x” set EDGES {1 3 5} set CLK_PHY_PORT “clk4x” set PERIOD [expr 0.833 * $TOOL_TIME_SCALE * $LIB_TIME_SCALE] set PHY_CLK_PERIOD $PERIOD set PHY_HALF [expr 0.5 * $PHY_CLK_PERIOD] set PHY_QUARTER [expr 0.25 * $PHY_CLK_PERIOD] set CTLR_CLK_PERIOD [expr 2 * $PHY_CLK_PERIOD] set PHY_DDL_CLK_PERIOD [expr 0.2 * $TOOL_TIME_SCALE * $LIB_TIME_SCALE] create_clock [get_ports $CLK_PHY_PORT ] -name dummy_clk4x… 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 »