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66 Threads found on Multicycle Path
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 (...)
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 (
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
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?
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 (...)
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?
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 (...)
hello all, i have doubt regarding, how all data from fast clock to slow clock path recivced correctly at capture flop? suppose clock period of fast clock = 10ns and slow clock = 25ns then in that case launch clock is fast clock and capture clock is slow clock. i think data of some edges from launch clock may not captured by capture clock
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 (...)
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
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?
Hello All, How to define constrains on the synchronizers during the synthesis and STA? Besides the set_false_path, should be set_multicycle_path be defined as well? Why? Thank you!
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 (...)
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.
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 (...)
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 (...)
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.
hi all, For eg : a path between two flops (FF1 - FF2) has a big comb. logic which gives my required output at 3 capturing clock of FF2. since there exists a multicycle path between two flops if i break my comb logic and use pipelining of same two regs this a correct method ? Eg : FF1 - comb - FF2 Changed : FF1 - (comb1 - FF) - (comb
Hi guyz.. What is multicycle path? and is it similar to false path?? thankx
I Believe if there is a generated that is derived from the source clock then its sure that the clocks cannot be asynchronous. And u need to setup a multicycle path because the data may not be captured in 1 clock cycle because ur generated clock is 8 time slower than the original clock. So i suggest take help of designers and try to confirm what MCP
Hi, I am not able to find any link to download fishtail focus tool to determine false path and multicycle paths in your design. Has anyone downloaded the tool and used it? Is it free or free for limited time? Please send me personal message if you know where to download it from.
How to find unconstrained paths in design.I mean what are the reasons for unconstraing paths other than false path or multicycle path.
If we send data from one clock(say slow clk) domain to other clock domain(say fast clk), then what kind of constraint we have to give while doing synthesis or STA. Please refer the diagram given here. There is a general guideline that when ever the data crossing the clk domain in your design, give cosntraints set_false_path -from clk1 -to clk2.
Hi All, How to identify the Multi cycle path and the False path in the design. do we need to identify after the Synthesis stage DC tool it self will recognize and through as warning or error. At what stage in the asic flow this multicycle path and False path are identified. How to fix this Multi cycle (...)
Hi All, How to identify the Multi cycle path and the False path in the design. do we need to identify after the Synthesis stage or the XILINX (fpga tool) tool it self will recognize and through as warning or error. At what stage in the FPGA flow this multicycle path and False path are identified. How (...)
hi, Set the path to multicycle path. Thank you.
Hi Badola, You will put the add slow cells to those flops which are the startpoint s of "false path" and "multicycle paths". During STA you dont do an analysis for the false and the multicycle paths, so you will not want to use these paths for detecting faults. So you put a "add slow (...)
synchronizers, or paths where signals which cross clock domains are usually added as false paths in the constraints. a good example of multicycle path would be a pipelined path
The DFT guy will also want to know about your multicycle path, because ATPG has no knowledge of timing, it will generate patterns that assume that all paths resolve within the clock cycle. If the scan patterns are then simulated or run on the ATE, they will fail, unless they are run slower than your longest flop to flop (...)
I dont think there are any tools to do that. Identifying false path and multicycle paths require human intellegence. False path in some cases may be identified automatically, but multicycle path is a design issue, where the designer may approve some paths to take more than a (...)
Dear Designers, my 2 cents... You will find a very good article regarding Static Timing analysis in the below mentioned link. In this you find good articles about falsepath, multicycle path and source synchronous paths explanations and scenarios.
How to apply multicycle path on a data to data check. i mean when the data to data check is checked it is checked it is checked as multicycle path (say multicycle of 2). But since the data pins are also constrained wrt to clock pins, the multicycle path set on the data to (...)