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39 Threads found on edaboard.com: Set False Path
Hello all , There are times, when I am not allowed to change the RTL, and all the clocking structure in the design are already optimized. Still I face situations where I have negative slack ( setup as well as hold ) Some times by trying few strategies in Vivado, the tool solves the timing violations, but what if it doesn't ? Question 1 : Ca
Hello All, I wanted to know what all are the options I have when I have to fix set up violation in a design ( with no hold time violation ) without changing anything in rtl. What are the stratagies I can use ( not the tool stratagies of vivado ) Thanks
Hello, MCP is multicycle path during capture only as we are running shift at low speed. If we provide multiple cycles, it will detect the non scan flops in between 2 scan flops. It will detect MCPs also, Suppose we set sequential depth as 3, it will detect MCP with 3 cycles and also non scan flops which are in between scan flops.
There are two clock made constraint as create_clock. If I don't set false_path about these two clock. After CTS, are these two path balance ? What action does CTS handle false_path constraint ? For CTS, these two clocks are treat as independent and have not balance ?? Thanks.
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 ).
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_
a false path is one that would usually be analysed by the timing analyser, but for whatever reason, you dont want it to do it. An example would be signals that cross a clock domain boundary, or maybe something that you set once and doesnt change for a very long time, and having a "failing" path wont really have an effect on (...)
in clock domain crossing, you set false path for hold while doing synthesis because two clocks are asynchronous and timing cannot checked. But you set set_max_delay and set_min_delay on these paths. so that data should reach after specified delay.
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 more elaborate (...)
Is it necessary to set false path during FPGA synthesis? How can it be done if it is yes? Regards
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
Hi, I am confused which should be set for asynchronous control signal, false path or recovery and removal constrain? Could you tell me how to choose and why? Thanks!
Not Always. CDC(Clock Domain Crossings) analysis required very much in bigger SOC's. If these clock domains are not interacting in any of the functional modes, you can always set false paths. If its interacting, you cant set false path untill and unless , you have any other mechanisam to (...)
First set the path as false path between the clock domains. Then 1. If there is no data going through between these clocks then fine no problem. U can carry on with the STA. 2. If not then u need to have FIFO design with sufficient depth, so that there r no data lost. Which is normally written in the verilog code itself by (...)
If I understand your question correctly, you are asking if input to output path can be set as false path. This can be or can not be set as a false path depending on the design. Generally these paths will be analysed with constraints applied at input and (...)
I want to synthesize a Clock domain crossing design. Do i need to set a false path from clk1 to clk2 as explained by jbeniston?
check this set_clock_groups notes - Altera Forums
Hi all, In my design i have scan flipflop contains sd(set),rd(reset),clk,si(scan input),q(output),d(signal input).sd(tied to 1) For static signals like SD and all other static signals how the tool taken care when the Timing closure stage.whether it is taken as a falsepaths?.
i dont know what is RTDC-115 and how to constraint asynchronous pins of sequential cells?? should i set what kinds of constraint on these pins?
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 (...)
At Speed test uses two high speed functional clock pulse to test the delay of the combinational lgoic between registers. However, some combinational logic will take more than one cylce to propagate. So the two clock pulses are not enough for these logic. usually, we will set false paht of these paths. Another way is to use pipelineing (...)
Hi, If the clocks are from the same source(when you say you are generating the 1MHz clock from 8 MHz then these two clocks should belong to the same domain) you need to set the 1MHz clock as a derived clock and define the corresponding parameters. When you do this the tool will automatically check the timing of the signals that cross the freq do
Could anybody give me a complete conclusion in what stances should we set false path? As I know, 1) different clock domain; 2) the path don't need to do timing analysis.
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
Hello, Can anyone explain in more details about the question below?. Thanks in advance. 1. How flattening during synthesis can improve the speed? 2. When set false path is used in synthesis? 3. When set multi-cycle path is used in synthesis?
when including the IO PAD module ,the delay for some pad (e.g. reset_pad)is too large in critical setup timing path .Therefore,the violation is too large.can anyone help me? Thanks!
yes, just set the path as false path will done the job
exception is mainly include false path and multi cycle path. false path are set for any logic which not required to analyse timing. and multicycle path is that path which required more than one cycle compare to launch clock to execute its function
You can go to to see example commands to set false path.
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 (...)
Hi, everyone, We know, DFT Compiler inserts lockup latch between adjacent scan FFs if they are triggered by different clocks and the test clock waveforms are the same. Use the command set_scan_configuration ?add_lockup ture However, in this case, how can we set false path when doing test mode STA ? Now, we use the (...)
"set_false_path" is the command input could be chip inputs and register inputs and o/ps could be chip outputs and clocks.
For setup violations.. check the critical path and try to break that path by inserting a register between that combination logic.. or add buffer to increase delay of clock path to second registers.. For hold violations.... check the critical path where u get minimal propagation delay.. add buffer or (...)
if 2 clocks are asyn, why can't we set them to false path?
in sta,if two clock domain is asyn ,we can set false path to them. if two clock domain is syn, maybe fast to slow,maybe slow to fast, how to constraint the path between them? i see a conculsion ,but i don't understand what it mean. just like in the picture.
If the control signal is a static signal, you can just set it as false path to disable timing check on this path.
In script 1 you need to set false path between clocks! This will solve the problem!
#---------------------------------------------------------------------------- # set option values set verbose 0 ;# 1 for verbose source commands set noscan 1 ;# false path the SCANEN input set signoff 0 ;# Use post layout netlist and (...)
If you've done a good job in handling the exchanges of data between different clock domain, perhaps using an asynchronous fifo for that. Then you can safely set false paths between the asynchronous clocks.