[SOLVED] the max_transition and max_capacitance vio?

[irun2]

Hi there!
This is a mcu design and not very large scale. I've encountered a problem when doing synthesis work.
No matter what I try, like using -incremental and -map high options, the Max transision violation stays there!

max_transition
Required Actual
Net Transition Transition Slack
-----------------------------------------------------------------
mcu_otp/RegRdAddr[0] (dont_touch)
4.50 15.24 -10.74 (VIOLATED)
max_capacitance
Required Actual
Net Capacitance Capacitance Slack
-----------------------------------------------------------------
mcu_otp/RegRdAddr[0] (dont_touch)
0.16 0.65 -0.50 (VIOLATED)

report_net report below statistics:
Attributes:
dr - drc disabled
c - annotated capacitance
d - dont_touch
i - ideal_net
I - ideal_network
p - includes pin load
r - annotated resistance
h - high fanout
Net Fanout Attributes Capacitance Driver
--------------------------------------------------------------------------------
mcu_otp/RegRdAddr[0]
65 d 0.65 mcu_otp/pwd1/decode/U144/Y

I've tried remove_attribute mcu_otp/RegRdAddr[0] dont_touch and compile again, but without luck.

How can I get rid of those violations like capacitance and transition? Should I manually add buffer to that pin? Or leave it to P&R guys?

 

[shobhit]

Frnd

Most probably the tool is not able to optimize the net for better transition because there is a dont_touch true on the net . You cant remove the attribute instead you need to set the dont_touch attribute as false on thet net using the set_attribute command, once it is made false the tool will optimize for transition violations, further during synthesis you can give preference to fixe drv (transition, capacitance) violations, so tool will give more stress to improve transition violation.

 

[irun2]

Thx! But the high fanout are still there and at last I added buffer manually...

 

[rca]

the fanout violation could waived if cap/trans/setup/hold are ok. the fanout does not impact the timing. If you look at the liberty file, only the cap & trans are used in the timing table. you could forgot the fanout.