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report_timing after clock tree synthesis shows the same clock to be ideal on capture flop while propagated on the launch flop

Hello Everyone,

After my clock tree synthesis is done, I use "report_timing" command to report the timing paths. I see some of the clocks in the design to be ideal on the capture path while being propagated on the launch path. Could there be some setting I am missing which has resulted into this? Below is one of the failing paths:

Path 219: VIOLATED (-2.235 ns) Setup Check with Pin digtop_scan_inst/dsp_top_inst/ucdsp_subsystem_inst/u_ucdsp_mem_wrapper/u_ucdsp_yram/CLK->WZ
View: func_QC_MAX_CUSTOM_W_150_1.35_setup
Group: reg2reg
Startpoint: (R) digtop_scan_inst/dsp_top_inst/ucdsp_subsystem_inst/u_uCDSP/inst_reg_ACl/reg_val0_reg_25_/clk
Clock: (R) DSP_CLK
Endpoint: (R) digtop_scan_inst/dsp_top_inst/ucdsp_subsystem_inst/u_ucdsp_mem_wrapper/u_ucdsp_yram/WZ
Clock: (R) DSP_CLK

Capture Launch
Clock Edge:+ 12.000 4.000
Drv Adjust:+ 0.432 0.432
Src Latency:+ 3.286 3.995
Net Latency:+ 0.300 (I) 2.436 (P)
Arrival:= 16.018 10.862

Setup:- 0.734
Uncertainty:- 0.300
Cppr Adjust:+ 0.709
Required Time:= 15.692
Launch Clock:= 10.862
Data Path:+ 7.065
Slack:= -2.235

Please note the above highlighted line which shows the net latency. The clock DSP_CLK is reported to be (I) ideal for capture while it is reported to be (P) propagated for launch path. Have I missed some attribute setting?

Chetan B S over 7 years ago

Hello,

Please check on any set_clock_latency applied on DSP_CLK

You can also check the propagation of the clock to the launch and capture flop clock pins to check for any blocking.

Regards,

Chetan B S
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Gyan1623 over 7 years ago in reply to Chetan B S

Hi Chetan,

Thanks for your response. The clock propagation used to stop in the capture path after crossing initial few gates. Below settings before reporting the timing helped resolved the issue:

reset_clock_tree_latency *

reset_clock_latency * -source

reset_clock_latency -source [get_ports *] -clock [get_clocks *]

reset_clock_latency -source [get_pins * -hier] -clock [get_clocks *]

Thanks and Regards,

Gyan
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Chetan B S over 7 years ago in reply to Gyan1623

Hello,

Good to know that it is resolved now.

Regards,

Chetan B S
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