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If your design has a flip-flop with high fanout, the fanout-induced delay may cause trouble meeting your timing constraints. The synthesis software may detect this condition and automatically duplicate the flop so that each one drives fewer loads, and therefore has lower delays.
After synthesis of ISE, you can see the critical path from the report.
Hi, Suppose timing constraints are not met in the design,What are the other options? (either in synthesis or physical domain)
It doesn't matter what kind of synthesis tool used. Since almost if not all synthesis tools support timing constraints in SDC(Synopsys Design Constraint) format. So you can still use these 2 books as a good reference. ------------------------------------------------------------------ By thw way, lots of concepts of (...)
See KEEP in the constraints Guide. For example: module top (in, out); input in; wire chain; // synthesis attribute KEEP chain TRUE output out; assign {out,chain} = {chain,~chain,~in}; endmodule
Hi anajali, so ur post synthesis simulations failed. but again, whether the behavior simulations were working correct?
timing constraints is very important for synthesis. you can refere to those books of "timing" for detail.
Gate-level simulation can help to identify those timing exceptions, such as 1) false_path(s) ex. cross clock domains 2) multi-cycle path(s) ex. re-timing by synthesis tool Due to these timing exceptions maybe not correctly described in the timing constraints for STA.
For 2nd question: SDC should be used for synthesis. So if you just report the power after the logic/power optimization, then SDC file is necessary. Because the synthesized netlist may have large difference from the one w/o timing constraints. If the constraints are so loose, then maybe the netlist does not have much difference in (...)
Hello Freinds, Here i have a new doubt, as i am not well experienced at synthesis level. Here while giving constrains to a design at synthesis level, such as clock freq, input delay, output delay, flip-flop delay's etc, For clock freq it is well known according to the protocol frequency is the constrain, but what about the other delays s
Apply all constraints on the core and synthesize it without IO pads. After synthesis insert IO pads into the netlist using scripts or manually. But if u r inserting PADs into RTL before synthesis, then put a dont touch on all IO pads, and do synthesis. better to follow bottom-up compile stratagy to acheive better (...)
i wud like to stick on with Sparc's suggestion. Re-synthesising will b performed, when u feel ur synthesis were initially not giving good results. at this pt, u might have to put a tighter constraints and change the options available with synthesis tools
WHen synthesising , design maybe 10% overconstrained. you say it is far away. I think , you'd better re-synthesis it to meet your time constraints.
Search the Xilinx constraints Guide for RAM_STYLE DISTRIBUTED. Here's a Verilog example: reg myram ; // synthesis attribute RAM_STYLE myram "DISTRIBUTED"; Good luck!
pls check the discussion - " How to write a script for synthesis" In that i have uploaded a pdf ... dctut.pdf download that is enough for starters .. it also will tell u about common constraints in synthesis
It seems your design doesn't met the setup/hold requirements for related parts. Try another constraints set for synthesis or insert some buffers to avoid setup/hold errors.
Hi, jelydonut: Please check your skew/uncertainty from RTL to gate level synthesis script(s). You might need to find out the delay by yourself. However, the best way to solve your problem is.... checking with your front-end designers... :roll:
Hi, Shockie I think the same result means that the result timing is under your constraints, that's OK. But not means the detail circuit is the same between twice synthesis. In my design ,each time I find some difference can happen, but the function and timing is correct. we give the same constraint and then get the sam