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False Path Constraints

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26 Threads found on False Path Constraints
I would suggest to have the following constraint first. 1. clock period 2. input delay 3. output delay 4. clock uncertainity 5. clock latency 6. set load 7. set input transition 8. false path / Multi-Cycle path ( between the clock domains if any ).
All constraints are having specific to a condition , one constraint can't replace another. In Hardware , there are many signals and sometime it might be possible when you have apply more then one constraint on same signal , in that case, tools will look for order of precedence and final constraint will be applied having higher priority. Fals
well, in small design, this argument requires so many time that it is impossible to have a result. in big design it is unusable. in all case, the false-path should be added if the timing could not be reach. I means if the timing is fix without any constraint, that's better for the run-time of the backend flow, avoid any constraints if (...)
Hi All, What Timing constraints should be applied to Synchronizers? Should it be false path? MultiCycle path? Max Delay? Etc? Thank you!
The basic questions will be on 1. Clock constraints (master clock, generated clock, clock skew, jitter, clock network delay, source delay) 2. Input and output constraints 3. Virtual clock and the use of it 4. false path and multi cycle path. How will you identify them. 5. How will you fix setup and hold (...)
Hi All, I am using Xilinx's Vivado 2013.3 for generating the *.bin file. There are a lot asynchronous paths in my design. for example if I have grouped the signals like : # in CLK1 domain set GROUP1 ; set GROUP1 ; set GROUP1 ; # in CLK2 domain set GROUP2 [get_cells {sig_
Synthesis will never indicate if a apth is multicycle or need a false path constraints. Only the RTL designers could indicate which path could be relax with a multi cycle path constraints. The synthesis engineer could report the worst path with the current constraint (...)
Just want to know the opinion of the forum. Is it preferred to use exactly the same set of constraints for both synthesis using DC, and STA using PrimeTime? Does the synthesis tool use the false path specifications, or max transition constraints? Or can we use a simpler constraint file to do synthesis, and then use a (...)
hai friends i have a setup violation in a path starting in the Q pin of a flipflop followed by some logic blocks and ending in the D pin of the same flip flop how can i over come this can i set false path or multicycle path help me........... thank you
If they are not false path, you need constraint it. Even it's false path, you'd better use "set_false_path" to clearly clarify this in your contraint file. This is for easy understanding of the whole design by others.
Hi, Check out the timing constraints for the specific Vendor software. You should have something for false path. For Xilinx ISE, TIG - Timing Ignore is the timing constraint which is useful. If you use this then, path will be ignored and you won't get any error for this. Hope this helps you out
Tool should give warning in this case and path should be considered as false path. What is the need of setting max delay on a false path.?
Can a path that starts at an input port of the chip and ends at the output port of the chip (I-O path) be fasle path? Please let me know on what reasoning thst I-O path be a false path.
I will take this in priority wise the constarints. As false path has more priority than multicycle path it would take the path as false path and not do the timing analysis there. It will report though, so that u know u have made a mistake and u can correct it. For ur information this is (...)
hi it seems synpify ignores my false path constraints. i set up false paths: # Clock to Clock # define_clock_delay -rise {fpga_pciclk} -rise {Inst_businterfaces.ldt_clk} -false define_clock_delay -fall {x32_clk_better} -rise {x2510_clk8} -false (...)
Hi, I have written a tutorial on dc, I guess it will help you. It gives actual commands used to set constraints, and the page also gives example to set false paths, and much more. hope it helps, Kr, Avi
like setting it as a false path ?
false path is an unused path which is not considered during timing analysis for example take a has so many signals conected for its interneal use only but when it comes to timing analysis it is not be going to use so that is the false path.......... like G1, G2_n or something like that u will see right or (...)
read in design set input constraints like drive strength and arrival time. set output constraints like load and output delay times. define all clocks define any false path and multi-cycle path in the design. set clock skew and jitter tolerances. define all input/output timing relationships between (...)
Yes , SDC file contains timing exception paths i.e false path ( set_false_path ) , multicycle path ( set_multicycle_path ) which is used by downstream tool like STA tool etc.
set_false_path is not causing your problem, there might be a 'set_dont_touch_network' on SCANEN somewhere in your constraints
During synthesis, we apply a dont_touch_network and false_path on the reset ports because they will be buffered using CTS in the P&R. When should we remove these constraints - at entry into the P&R tool or after floorplanning/placement and before CTS?
I think those are false path , don't need to fix it. When your chip work the scan_enable will tie to high or low and will not change . And the scan_enable signal don't need use clock to catch, it is async with clock.
First, you should ensure it's a true violated path. So you should dive into RTL and documents, maybe talk with front-end designer. In report_timing, you are able to use -justify to verify ture or false path. Please refer to documents for detail. As a professional, you are not allowed to modify the constraints w/o any true (...)
For your example: suppose you have a 10 ns clock period and a multiplier that takes 13 ns to calculate the answer. If you make your control path that it launches the multiplication at clock edge @ time = 0 ns. If you don't clock (clock enable=false) what's coming out of the multiplier at time = 10ns, and clock the result in at time = 20 ns, you
false paths are paths which you want to exclude from STA analysis. Following are examples of false paths: 1. paths between Async-Clock Domains: This is taken care by demetastabalization circuits and are ignored in STA. 2. paths that exists in circuit but no combination (...)