If the pattern simulation failure occurs, we need to analyze the failure and need to do the necessary changes in the ATPG stage like SPF modification to clean up the simulation failures. If any Error or severe warnings occurs at ATPG/vector generation stage, it can either be solved at the same stage, else we need to jump to the SCAN stage for the required changes which help to clean ATPG issues. Once the design is ready with scan inserted netlist, test vectors will be generated and the same vectors will be used for simulation. Simulation/Pattern validation plays a vital role in DFT, in order to examine the vectors generated by the ATPG tool. Refer below figure to check the interdependency of all the stages. Simulation is the later stage after ATPG, for the validation of the patterns generated in different formats.Īll the stages are interdependent on each other. ATPG is performed on scan inserted design and the SPF generated through scan insertion. IntroductionĪTPG (Automatic test pattern generation) is the process of generating the test vectors for the particular test mode to check the manufacturing defects, which is further used by simulation tools for validation. Keywords: DFT (Design for testability), ATPG (Automatic test pattern generation), Simulation/Pattern validation, SPF (STIL protocol file). In this article, we are going to understand how we can solve the gross simulation failure by understanding and editing the SPF skeleton at the ATPG stage. Based on the matching responses of the circuit, the goodness of the chip will be defined, which in the end concludes the quality of the chip. Simulation’s pivotal role is to check if the binary response applied as an input that matches the values at the output response of the chip. Simulation Failure debugs and its solution:ĭesign For Testability(DFT) adds an extra Hardware/Structure in the existing functional design also called MBIST/Scan insertion to get controllability and observability of the design to make it easily testable after manufacturing i.e., post-silicon Soc testing.equivalent to sequence s1b ( posedge clk1 ) s1 # 1 1'b1 endsequence ( posedge clk1 ) s1b # 1 ( posedge clk2 ) s2Īs to why? Amybe to keep it simple as there are other ways to clearly express the intent. The following should be legal though ( posedge clk1 ) s1 # 1 '1b1 # 1 ( posedge clk2 ) s2 For example, if clk1 and clk2 are not identical, then the following are illegal: */ ( posedge clk1 ) s1 # 2 ( posedge clk2 ) ( posedge clk1 ) s1 intersect ( posedge clk2 ) s2 Sequence_expr # 1 `true |-> property_exprĪp1 : assert property ( ( posedge clk1 ) $rose (a ) |=> ( posedge clk2 ) b ) // equivalent toĪp1 : assert property ( ( posedge clk1 ) $rose (a ) # 1 1'b1 |-> ( posedge clk2 ) b ) // same asĪp1 : assert property ( ( posedge clk1 ) $rose (a ) # 1 ( posedge clk1 ) 1'b1 // clock flow through |-> ( posedge clk2 ) b ) /* 1800'2017 Differently clocked or multiclocked sequence operands cannot be combined with any sequence operators other than #1 and #0. Sequence_expr |=> property_expr // is equivalent to: Real Chip Design and Verification Using Verilog and VHDL($3) ** SVA Handbook 4th Edition, 2016 ISBN 978-1518681448ġ) SVA Package: Dynamic and range delays and repeats Ģ) Free books: Component Design by Example See the explanation with an example that I provided in my SVA bookįor training, consulting, services: contact The nearest possibly overlapping tick of the second clock, where the second sequence begins. ( posedge slow_clk_A ) $changed (A ) |-> # 1 ( posedge fast_clk_B ) $changed (B ) // is same as ( posedge slow_clk_A ) $changed (A ) |-> ( posedge slow_clk_A ) 1 # 1 ( posedge fast_clk_B ) $changed (B ) // The sampling is at the nearest strictly subsequent tick of the second clock, // vs ( posedge slow_clk_A ) $changed (A ) |-> ( posedge fast_clk_B ) # 1 $changed (B )
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