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94 Threads found on Multicycle
Hi All, I have input delays set as greater than the available clock periods. For example, in my constraint file Input delay for a pin is set as 25.5ns and I am using 8 ns period clock and the path has multicycle path of 3 periods. So I m getting violation in preCTS stage as the delay is high compared to the clock period. I
See this pdf on multicycle paths multicycle paths are useful if you have a large combinational circuit that has a propagation delay that exceeds the clock period and you either can't (e.g. encrypted IP
the example above doesn't work without a multicycle constraint. I don't see why it wouldn't work without the multicycle constraint, this might have been the case in a much older technology node than today. At 50 MHz this will make timing on any part in that Vivado can implement without multicycle constraints (
An excerpt from TrickyDicky's post in #5 If you then get really stuck, look into logic locking specific parts of your chip (ie. assinging specific entities to specific regions of a chip so that they have priority there) and ensure you have specified all false and multicycle paths in your SDC file. And as a final case, specify max delay c
Hi, Can anybody tell me the advantages of using Asynchronous FIFO when we can do the clock domain crossing using multicycle path cdc (synchronizing control enable signal and holding the input data for mulitple cycles ). why go for the pains of creating a fifo and verifying it also adding significant gate count to the design. -abhinavpr
I ask this because, when we write data into the asynchronous FIFO, the data input to the FIFO and FIFO write are in same clock. So no clock domain crossing occurs at this point. When we read data from the FIFO, the read clock and the data fed circuit will be in same clock domain. Again, no clock domain crossing!! data input to th
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.
Hey, False path constraint is much more strict, as you are saying that paths between launching and capturing flip flops will not exist, may be due to some architectural condition. Hence, tool will not time those paths. I guess SCP is single cycle paths. I am not sure about SMT. Thanks, Abhishek www.ed
In which stage of the design flow we get an idea about the false paths and multicycle paths in the design? Which tool will report them? In RTL level, we are left with the logic of the design only and we will have no idea about how the tool will synthesize different paths in the design. The tool will synthesize the design according to it's algorit
I suppose you are using some tool like Dc compiler and you want to specify a multicycle path constraint for a design...right ???
A multicycle path is one where the signal generated by the source need not be sampled at the destination the very next cycle. The destination usually has more than 1 cycle to sample this signal. What kind of constraint do you want?
Hi, suppose we want to create data path of multicycle MIPS processor.our clock frequency is 400MHz and we want to execute every instruction in minimum time.(delay of Controllers and multiplexers is zero) Instructions to be Implemented: addu, addui, and, andi, beq, bne, lw, sw Memory: Address to Read-Data propagation delay: 9 ns Write to Rea
Hi Is DesignWare's multiplier needed to multicycle path? I want to use 3stage multiplier but I don't know about how much it needed clock to result. And should I have to constraint to multicycle 3 depth to here?
Hi,does anyone know how to fix this error?. I'm trying to create multicycle processor using verilog. During the test bench simulation in modelsim, it gives 113073
112126 This image comes from Altera AN433. As we can see, AN433 requires to constraint the Opposite-Edge Capture Center-Aligned Input with multicycle and false path exception. However, in my opinion, we just have to constraint that with false path exception which would remove the analysis of same-edge data transfer lab
It the responsibility of the designer to communicate it to the synthesis engineer if there are any multicycle paths in the design. The designer is the only person familiar with the design. The synthesis engineer is unaware of the design details. Once the synthesis engineer is aware of multicycle paths, he can form the necessary constraints and use
Hi. I have some question at synthesis. When you have been synthesis, did you always give or receive information like multicycle path -2? I mean when they have getting more bigger design, they are miss or even don't know information for synthesis. So how can you overcome this issue?
Hi, During stuck-at testing, what will happen to false and multicycle paths from the functional logic. Will stuck-at testing take them as faults? How does ATPG tool handle false and multicycle paths?
False path is more restrictive, and then this one has priority over the multicycle path exception. Same idea for set_max_transition, you could not relax with this command, the tool will use the most constrainted value provided (or not) by the liberty or the constraint.
Hi All, What Timing Constraints should be applied to Synchronizers? Should it be False Path? multicycle Path? Max Delay? Etc? Thank you!
Hai friends i have doubt whether can i set a multicycle path of setup value 0 set_multicycle_path -setup 0 -from xxx -to yyyy -end will i be able to meet setup and hold for this path if setup is checked at 0 how should i give a multicycle path for a hold check Thank you
Hai ramesh you can set multicycle path for both the conditions i.e from slow clock to fast clock and from fast clock to slow clock for the condition from slow clock to fast clock set_multicycle_path x -setup -from launch_clk(slow) -to capture_clock(fast) -end ---> which will add multicycle to the capture clock for the condition from (...)
what is your issue? if your design does not met the timing, you could analyze if some path need multicycle constraint
I have a chunk of combo logic (synthesizable netlist) where the shortest path is 1 ns and longest path is 7 ns. My clock is 5 ns but I need single cycle throughput. If I were to pump input every clk and capture 2 cycles later at every cycle, the shortest path will have a problem, and longest path may have problem in best corner. Is DC able to
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
Is there a limit on the number of multicycle paths that can be used in a design??
In the original example, the delay isn't properly implemented. Although I agree completely with Tricky's suggestion of doing everyting in pipeline, a multicycle delay can be of course implemented. We have to be aware of a certain delay range of n1 to n2 cycles to get the result from the combinational logic. So what you can do is - register the inp
Learn about the following things... 1. Clock definitions 2. Exceptions (false paths, multicycle paths) 3. case analysis 4 How to switch b/w func & scan modes 5. the modes of STA 6. the use of libraries in Synth & STA, get to know what all info is there in .libs 6. What is spef & why are different exreaction corners necssary. etc.. etc... there i
Hello All, In the case of Mullticycle path, the setup value is more than the hold value, however if we consider multi clock domains in the multi cycle path, can setup value be less than hold value? Please provide your views.
What about multicycle paths?
I have even seen designs that work without setting false path as well. You have to see this I am also pasting the script that does the real synthesis. "Note there is no false path or multicycle path command." ##############################
Increase the clock period to remove set up time violations. Check for multicycle paths and false paths. Filter both of these. I am not sure about asynchronous signals. Just try nominal case for STA first
It depends if read is single cycle or not. Usually it is so it is correct. If read is multicycle read the you have to keep we asserted for that many cycle. chip select signal should behave the same. Hope it helps
Synthesizer will optimize logic in the same way as for singlecycle path, the only difference is that it will try to meet timing constraints for smaller frequency. Yes, you are rightm it should be sampled every 2 clocks (or every 3 or ... it depends on how many multicycles you have defined).
can anyone explain me, why hold was not calculated at default edge? there is no definitive answer for this, because it depends on the logic. In some design, you don't want the launched data to get captured by the same edge, which is most likely case, but in some multicycle situation, you may not want the data t
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 the priority for PT 1. set_false_path 2. set_max_delay and
You may want to split a clock to drive different blocks which the paths are not synchronous between and you want to set false/multicycle paths on.
If it is a multicycle path
Any STA tool will try to find the LCM of the 2 clocks and time the path using that clock your case, its as barry mentioned, you have different clocks and would need a FIFO or synchronizer ..If its source synchronous clock , you might not applying multicycle path, you are only avoiding th problem here as STA will not
Constraint problem! Correct and timing report looks OK.
There are many types of constraints - false, multicycle, set_input_delay, set_output_delay, etc Can anyone give a complete list of the order is which constraints have priority? Thanks,
Can anyone tell me about multicycle hold analysis? Does it affect the frequency of the chip?
In a multicycle path of two cycle set setup is checked at the second cycle and hold is check at first cycle. Why?
Hi Yang, I strongly believe PowerCompiler definitely will support to break the cross clock domain and multicycle path in the designs. a). Better refer the Power Compiler manual for the exact command lines. b). Break the Clock Gate path and exclude from the timing check and do the STA/Power Analysys. Try to execute Dynamic Simulation (GLS)
Agree with lostinxlation! Another point is : not all the multicycle path contain many conbination logic on data path. Someone may specify the multicycle path for some special requirement. For example, multi-frequency design, Source Syncronous Bus design. In that case, you should be careful about the hold violation in the multicycle path.
Hi, as you I do not think that hold time is dependent on frequency do you have a fully synchron design? do you have clock domain crossings? do you have multicycle or false pathes? do you have clock divider? can you see in the simulation wavetraces that the hold time depends on the frequency? regards
if you believe it is a multicycle path, you can force the notifier of the endpoint DFF to 1'b0 forever or with a condition.
I am running synplify_pro and I have automaticaalt generated Fasle and multicycle paths are other tool. When I try to apply those constaint to synplify pro in .sdc file and do constraint check many of them flags error due to various reason. (1) FAM explorer changed register bitwidth and name also during FSM re-encoding. (2) Ig any register is
Hi, Does anyone know if negative setup or hold multicycle paths exist in design? If yes then why? Regards, Hemal
I have started exploring design compiler and have few questions and probably more to follow. It will be great if you can help me with your thoughts on them. 1) I saw that all the existing scripts in my company had specified multicycle paths for the signals which travel across clock domains. Why not false paths? 2) All the scripts had specif