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89 Threads found on Combinational Logic Design
b. Configuration logic Block (CLB) which contains the LUT to perform combinational logic.
A always @* block will never produce a flip-flop in a design it might produce a latch if there is feedback, otherwise you get a combinational blob. The reg keyword does not by definition produce flip-flops it only means the signal will hold state until changed by an assignment. This is part of the reason for changing it to logic in SV. (...)
Hi, Typical power consumed by a clock tree in the design is around 40-45% What is the typical or on an average power consumed by combinational logic cells in the design after pnr. Thanks
I can only answer it at a very top- (concept-) level. In order to reduce the negative slack, try to reduce the combinational logic between two the two registers (flip-flops). Or adding a pipeline can also be a solution. If your design is big, try out 'incremental compilation' to achieve timing closure for a particular partition that (...)
I am not using a clock. I have a universal logic cell which I'll use in the design of combinational and sequential circuits.
it's really dependent of your design, I means, a design with huge combinational logic, could have a lowest speed than the pad shift in/out, the pad sees very "high" capacitance which limit the shift speed.
This is a combinational full adder as there is no reference to clock. I am not sure what are you doing with the rst pin. The idea of doing an addition is combinational which has to complete within a clock cycle. But then the clock cycle will be very long as in case of ripple-carry addition. to make things faster you will have to put registers so th
Hi, I got the Loop exceeded maximum iteration limit. (ELAB-900) error in synopsys design vision. I am aware that it is not a proper usage of for in verilog. I am trying to generate a large combinational logic, that's way I need to use for loop in always@(*) statement. I was wondering if there is a way to increase the ma
well you did not find false path. your synthesis has some timing issue, so two possibilities: 1- the designer claims this path is false, so you could add this path to false in your SDC. 2- the designer claims this path is true, then you have a timing issue, to solve by pipeline or rewrite RTL to push combinational logic (...)
Hi, I write a custom library for synopsys design vision which only consists of XOR, NOR, and IV (inverter or NOT). My plan is to synthesize a combinational logic such that the resulting netlist has minimum number of NOR gates. I write the library as flows: library(and_or_xor) { cell(NOR) { area : 1000; pin(A
No issue after I added a fa.vhd file to the design. You do know this is a very large combinational circuit. Using Vivado it ends up with >60 levels of logic (LUTs) from a_in to y. Of course I didn't add any constraints to try and improve the timing. e.g. 105366 Regards
Hi all, I am using a low cost FPGA (EP2C5T144C6) and trying to compile my verilog code in Quartus II. The error message come out: Error (170011): design contains 5204 blocks of type combinational node. However, device contains only 4608. I have try to reduce some If,Else case but it has no big different. Is there any suggestions that i
Hello guys, Today I had a discussion about Verilog coding style with a senior engineer I personal prefer write combinational logic using assign For example, assign cnt_w = incr ? cnt_r + 1 : cnt_r; However, he said combinational logic should be coded using always for the following reason 1. Continuous assignment (...)
Roughly, in general, 1um net witdh could support 1mA. The question is how much high the pic of current is? Generaly if you have a clock design, after the rising edge all flops will consumme during the "skew" delay, and the combinational logic will change function of the new value in the flops. 1-Empiric way, you know the worst (...)
Can I set internal wire in my design as clock signal. Command define_clock has option {pin | port} But I need to use as clock internal wire from combinational logic.
hi can some one explain to me how design combinational logic with ic7483 output(c4,s4,s3,s2,s1) fpr comparator
My compilation is succesfull but the fitter report shows zero registers utilised. This is an absurd. This is just a fact. Your design doesn't define any registers. I'm not sure if you know what a register is? It's a DFF in constrast to combinational logic. You'll need a clock edge sensitive always block to infer registers, or equiv
The power consumption is when data changed, and the data change at clock edges, and due to the transition/clock tree skew, around the clock edges all flops could changed. And after that the combinational logic will be impacted as well.
can we include any combinational gates in scan chain? if the answer is no..please explain why should not we include? thanks in advance...
1- for our experience more than 10years, we design low power chip, the manual gated clock instertion is well know control than what it is done by the tool, or we do not see interesting power reduction based on our gated clock design. 2- yes, a combinational logic is added on the clock network, but the clock tree tool handle (...)