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tarkyss
Joined: 01 Aug 2005
Posts: 339
Helped: 16
Location: China
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 25 Jul 2006 14:25 case analysis in primetime |
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I am now doing STA with primetime
test enable signal is SCAN_MODE
one clock signal is generated in interior through a XNOR cell
another input signal of the XNOR cell is a signal that propagated from SCAN_MODE(it sticks to 0)
so i think the phase of the clock is the same with the input clock,
but when report_timing, one path start point is not from time 0,
for example the clock period is 20, we created the clock as
create_clock clock [get_port clock] -period 20 -waveform [list 0 10]
when report_timing, the start point is from the rise edge of the clock, that is time 10, not 0, why,(the end point of the path is the output port of the chip, the expected arrive time is 20)
I check the other input of the xnor with report_case_analyasis -all
it exactly is 0. so the case analysis signal does propagate to the xnor, why?
thanks
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steven852
Joined: 24 Apr 2005
Posts: 105
Helped: 1
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| 26 Jul 2006 0:14 Re: case analysis in primetime |
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| Is it help using report_delay_calculation command to see how those numbers come up?
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tarkyss
Joined: 01 Aug 2005
Posts: 339
Helped: 16
Location: China
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| 26 Jul 2006 5:31 case analysis in primetime |
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but there are lots of buffers between the input clock and the start point of the path,
can report_delay_calculation do that?
Added after 3 hours 19 minutes:
SORRY, my mistake
if one input of xnor is 0, the output invert with another input
sorry
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steven852
Joined: 24 Apr 2005
Posts: 105
Helped: 1
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| 26 Jul 2006 5:35 Re: case analysis in primetime |
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Well, it won't hurt to give a try, right?
Another way may be worth a try is:
get_timing_paths to form a specific timing path and then use get_recalculated_timing_paths to narrow delay.
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