This layout netlist is compared with the schematic netlist of the same stage for verifying whether they are functionally match or not. Opens:- Connections are not complete for certain nets. unmapped point (unreachable: all paths to outputs are blocked):(G) 9404 DLAT /sclrsclrb2_ebus_top_ebus_slave_to_gms_top_v2_ebus_controller_TIMEOUT_ERR_1_sqmuxa_0_a3_0_a2_i_o2_4_a_s_cZ/lc_ff. Conformal by default won't map them nor compare them. lc_ff is an instance name of the DFF ( Technology Specific ), Based on this we have following queries:-. Upon LEC comparison, unreachable points come up which was mentioned in my previous query. Ist case:-Synthesis netlist ( VQM's ) were generated using same tool with same version ( Synplify 8.2.0, Build 119R ). I do ***not*** recommend using it however. Definition Placement is the process of placing standard cells in the rows created at floor planning stage. we used netlists ( VQM ) to compare the Logic equivalences. Both are done at different phases of the PNR flow. Some of the LVS errors are: Logical Equivalence check (LEC) will compare the golden netlist with the revised netlist. The LVS tool creates a layout netlist, by extracting the geometries. For both the golden and the revised I have added the switch -insert_isolation. Parameter mismatch:- It checks for parameter mismatches. Unmapped point (unreachable: all paths to outputs are blocked):(G) 9409 DLAT /sclrsclrb2_ebus_top_ebus_slave_to_gms_top_v2_ebus_controller_TIMEOUT_ERR_1_sqmuxa_0_a3_0_a2_i_o2_a_cZ/lc_ff, Unmapped point (unreachable: all paths to outputs are blocked):(R) 9409 DLAT /G_4029_a_cZ/lc_ff. Some checks we have to perform soon after the completion of layout to check whether our layout works as designed. Hi , We are using conformal software Version 7.1 to perform LEC check.we used netlists ( VQM )  to compare the Logic equivalences. The typical causes:1) unused code in RTL2) spare gates3) disabled logic (e.g. Front-end covers the architectural specifications, coding and verification, whereas back-end involves the physical implementation of the design on the targeted technology node. Golden Netlist or pre-layout netlist is nothing but the synthesis netlist and the revised netlist or post-layout netlist is what we get after PnR flow. When compared between these two netlists we could see warnings Unmapped points due to DLAT's ( D LATCHES ). The VLSI design cycle is divided into two phases: Front-end and Back-end. Both the netlists are generated using synplify tool. Once RTL is released, the next step is to go for synthesis to get a gate-level representation of the design. If the two netlists match, then the LVS reports clean. Floorplanning is the most important stage in Physical Design. Else the tool reports the mismatch and the component and location of the mismatch. Hi DinakaranI don't think I understand your question. Please note that ***software version is same*** in both the VQM. Definition Clock Tree Synthesis (CTS) is a process which make sure that the clock gets distributed evenly to all sequential elements ... VLSI Guide A way to pursue your passion is a team of experts for more than 10+ years of industrial experience in the field of VLSI for inspiring the aspirants for upgrading their skills and cracking interviews. Are you concerned about the presence of those unreachables?I forgot one more cause of unreachables:4) clock-gating latches (with set flatten model -gated_clock turned on)The algorithm will undo the clock-gating, modeling the circuit as mux-feedback, but it leaves the latch there, dangling, hence unreachable. Shorts:-Wires that should not be connected are overlapping. These checks are known as Signoff checks. pre to post test)We still like to show you have them though because they could be a problem if they are unexpected.There's a way to make some of the warnings go away (set mapping method -unreach). This paper presents why LEC … Hi , We are using conformal software Version 7.1 to perform LEC check. LEC check is a signoff check and if it is failing (No Equivalence present) one cant’ tapeout. 'report message -model -verbose > model.rpt' should give you a better idea about what's going on with those keypoints.Chrystian. When compared between these two netlists we could see warnings Unmapped points due to DLAT's ( D LATCHES ). Then it report as parameter mismatch. A little more detail explanation: 2nd case:- One VQM was generated using Synplify 8.2.0, Build 119R and the other one was generated using Synplify pro 8.2.0, Build 119R. Hi , I had gone through "Tip of the month" on june 13 as per your suggestion. LEC starts as early as the front end and goes on till the final tape-out phase whereas LVS is primarily a backend sanity check. With respect to that, i would like to provide the details on set of experiments which were executed. 1, Are this messages are valid warnings?2, Is there any approach to reduce or eliminate these warning messages? Aishwarya Singh June 24, 2016 at 11:46 am. The changes may be very simple or complex. Understanding Logic Equivalence Check in VLSI | What is LEC? Definition Routing is the stage after CTS where the interconnections are made by determining the precise paths for each nets. If the value of particular component is different in layout and the schematic. We observed that, DLAT's are araised due to CLK pins of the instanced DFF  are grounded. Both the netlists are generated using synplify tool. With massively parallel architecture and adaptive proof technology, the Conformal Smart LEC delivers dramatic turnaround time improvements in equivalence checking …

lec check in vlsi

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