Its the sta engineer who owns the timing closure of blocksoc. University of california, san diego static timing analysis. Other delay budgeting techniques are described in 8. This video will guide you through the most commonly asked interview questions related to the static timing analysis which is the most commonly asked topic in interviews for digital profile. Mar 12, 2008 below are the sequence of questions asked for a physical design engineer. It checks the design whether it is working properly at specified operating frequency by checking the timing constraints predefined by vendor tool are meeting by the all timing paths across design. Najm, fellow, ieee abstractmanufacturing process variations lead to circuit timing variability and a corresponding timing yield loss. Answer to this question depends on your interest, expertise and to the requirement for which you have been interviewed. Having all of them in a single course makes it bulky. Basic static timing analysis concept input to sta tool setup time hold time slack clock latencies clock skew recovery and removal t. Click on the index in the left side window see picture above. Advanced static timing analysis using smarttime table of contents introduction complex and sophisticated clocking schemes and exceptions are currently used in low power and highreliability microsemi fpga devices. So we decided to have it in 3 parts and this is part i essential timing checks. Dynamic timing analysis has to be accomplished and functionality of the design must be cleared before the design is subjected to static timing analysis sta.
Here i am sharing very basic level interview questions on static timing analysis. Short circuit current state machine static timing analysis synchronoussetreset d. Basics of static timing analysis sta key points of sta determines worst case arrival time of signals at all pins of design elements does not test functionality does not distinguish between fun ctional and nonfunctional paths reduce complexity of analysis to increase volume of coverage. Static timing analysis among the combinational digital circuits is discussed in this tutorial. Dec 28, 2017 this video will guide you through the most commonly asked interview questions related to the static timing analysis which is the most commonly asked topic in interviews for digital profile. This method reports timing errors that functionally exist in the circuit and avoids reporting errors that occur in unused circuit paths.
Design issues pipeline pmos positive edge triggered puzzles rtl saturation setup time short circuit current state machine static timing analysis synchronoussetreset dflip flop the beginning threshold. Dynamic timing analysis verifies circuit timing by applying test vectors to the circuit. Static timing analysis comprises broadly for timing checks, constraints and library. Measuring the ability of a circuit to operate at the specified speed requires an ability to measure, during the. Static timing analysissta of digital circuits part 1. This approach is an extension of simulation and ensures that circuit timing is tested in its functional context. Obtain the prerequisite knowledge to attend the primetime. In comparison to circuit simulation, static timing analysis is.
Since g is directed acyclic, all the paths in g are simple. Our blended learning helps understand concepts mapped with open source tools. The microprocessor is a vlsi device before the introduction of vlsi technology, most ics had a limited set of. The speedup appears due to the use of simplified delay models, and on account of the fact that its ability to consider the effects of logical interactions between signals is limited. In sta, a combinational logic network is represented as a. The chip designers lack a central reference for information on timing, that covers the basics to the advanced timing veri cation procedures and techniques. Sta tool breaks the design down into a set of timing paths. Sources of timing variations channel length dopant atom count oxide thickness dielectric thickness vcc temperature influence performance yield prediction optimization design convergence management traditional corner based analysis suboptimum 0 100 200 300 0 0. Static timing analysis is a method for determining if a circuit meets timing constraints without having to simulate. Lattice semiconductor trace program difficult to cover all paths 9checks every path for timing violations simple timing checks 9minmax, clock skew, exceptions supports asynchronous designs 9synchronous designs only confirms function and timing 9confirms timing only. Aug 17, 2012 the static timing analysis tool performs the timing analysis in the following way. This kind of analysis doesnt depend on any data or logic inputs, applied at the input pins.
This method reports timing errors that functionally exist in the circuit and avoids reporting errors that occur in unused circuit paths the most common dynamic timing analysis is the socalled. Static timing analysis sta is one of the techniques to verify design in terms of timing. A lineartime approach for static timing analysis covering. So, it validates the design for desired frequency of operation, without checking the functionality of the design. I saw a lot of confusion with respect to setup and hold timing calculation. You apply these concepts to set constraints, calculate slack values for different path types, identify timing problems, and analyze reports generated by static timing analysis tools. Static timing analysis is a method of validating the timing performance of a design by checking all possible paths. For resources on the timing analyzer, see the following. No vector generation is required, no functionality check is done.
A timing path is a combination of all the timing arcs from a start point to an end point. Timing analysis is a method of validating the timing performance of a design. Assume a simple design comprising only a couple of handfuls of logic gates that end up being mapped onto four 3input luts a, b, c, and d. The timing analyzer is an asicstrength static timing analyzer that supports the industrystandard synopsys design constraints sdc format. This is faster than dynamic timing simulation because there is. Checks for timing violations depending on the constraints e. Static timing analysis also referred as sta is one of the many tech niques available to verify the timing of a digital design. First we will solve few examples which will give you an basic idea about these formulas, then in the last i will summarize all those in one place. What are some of the best resources to learn static timing. Nanosim, ultrasim crosstalk, v dd drop, electromigration analysis power analysis more detailed wire capacitance available for power analysis, iterate if there are problems. Apr 10, 20 static timing equations with skew and jitter. It will then outline issues related to statistical static timing analysis ssta, a procedure that is becoming increasingly necessary to handle the complexities. A false path, thus, does not need to get timed and can be ignored while doing timing analysis.
Static timing analysis is a method of validating the timing performance of a design by checking all possible paths for timing violations under worstcase conditions. Static timing analysis static timing analysis is a method of validating the timing performance of a design by checking all possible paths for timing violations without having to simulate. It considers the worst possible delay through each logic element, but not the logical operation of the circuit. A lineartime approach for static timing analysis covering all process corners sari onaissi, student member, ieee, and farid n.
The timing of the spark is measured as the number of degrees by which the crankshaft is short of bringing the piston in the timing cylinder usually no. Traditional corner analysis consists of checking all process corners combina. Clock setup minimum time interval between the assertion of a signal at a data input, and the assertion of a lowtohigh transition on the clock input. The chip designers lack a central reference for information on timing, that covers the basics to the advanced timing veri. Static timing equations with skew and jitter allthingsvlsi. Static timing analysis plays a vital role in facilitating the fast and reasonably accurate measurement of circuit timing. A timing path, which can get captured even after a very large interval of time has passes, and still, can produce the required output is termed as a false path.
An alternate ap proach used to verify the timing is the timing simulation which can verify the functionality as well as the timing of the design. It is based on a predetermined set of possible events of process variations, also called corners of the circuit. Verylargescale integration vlsi is the process of creating an integrated circuit ic by combining thousands of transistors into a single chip. Static timing analysis checks every path in the design for timing violations without checking the functionality of the design. In particular, the increase of delay variations has seriously.
Therefore you can say that static analysis starts above 100% and works towards 100% by detecting and excluding the false paths. Topics covered in static timing analysis sta vlsi junction. Scroll down the index window right side window, look for clock, then look for transition time. Through wires based on the characteristics of the wires and one can measure delays through probing the waveforms. For timing analysis, the startpoint to endpoint combinations are classified into path types. Vlsi design flow is not exactly a push button process. Static timing analysis sta sta checks the worst case propagation of all possible vectors for minmax delays.
What is latency or clock network delay or insertion delay. Jun 14, 2017 static timing analysis among the combinational digital circuits is discussed in this tutorial. The input to an sta tool is the routed netlist, clock definitions or clock frequency and external environment definitions. Welcomei8 i8 welcome synopsys 34000000s16 primetime. Statistical static timing analysis ssta ulf schlichtmann institute of electronic design automation technische universitaet muenchen munich, germany special session. Static timing analysis sta interview questions vlsi. This course will give an eagles eye to every timing check that is being performed in current industries for signoff. How to use sta tools to analyze the timing of synchronous digital asics. False paths are paths that are not possible or interesting in actual operation of the circuit. Dfmdfy design for manufacturability and yield influence of process variations in digital, analog and mixedsignal circuit design. Izumi nitta v toshiyuki shibuya v katsumi homma manuscript received april 19, 2007 with cmos technology scaling down to the nanometer realm, process variations have been increased.
Much faster than timingdriven, gatelevel simulation exhaustive, i. Dynamic timing analysis dta and static timing analysis sta are not alternatives to each other. Important questions like why do we need static timing analysis, why the timing should the meet, what. This is faster than dynamic timing simulation because there is no need to generate any kind of test vectors. To succeed in the vlsi design flow process, one must have. Below, we list some of the examples, where false paths can be applied. A2a static timing analysis is one of the most interesting topics in vlsi. Statictiming analysis is a determenistic way of computing the delay imposed by the circuits design and layout. The static timing analysis tool performs the timing analysis in the following way. Static timing means setting the timing with the engine stopped. This chapter will first overview some of the most prominent techniques for static timing analysis sta. Static timing analysis on the other hand check all path in the circuit even the false paths. Learning objectives after completing this course, you will be able to.
A pristine definition from one of the sta doc i have, static timing analysis also referred as sta is one of the many techniques available to verify the timing of a digital design. Below are the sequence of questions asked for a physical design engineer. Static timing analysis sta is a simulation method of computing the expected timing of a digital circuit without requiring a simulation of the full circuit highperformance integrated circuits have traditionally been characterized by the clock frequency at which they operate. The number of degrees varies from car to car again consult the handbook. Difference between static and dynamic timing analysis. Quality of the dynamic timing analysis dta increases with the increase of input test. While, the false state is represented by the number zero, called logic zero or logic low. Static timing analysis sta overview vlsi basics and. Courses taught by kunal ghosh vsd content is developed using a simple formulae to break the complex diagrams in such a fashion to understand each vlsi concept seamlessly. This page provides links to resources where you can learn more about the timing analyzer. For that you have to download a free kindle app on you. Mar 27, 2020 a2a static timing analysis is one of the most interesting topics in vlsi.
Vlsi began in the 1970s when complex semiconductor and communication technologies were being developed. Backend physical design interview questions and answers. Increasing complexity results in the need for more timing analysis capabilities that will be required for signoff and validation. Clock setup minimum time interval between the assertion of a signal at a data input, and the assertion of a. Static timing analysis interview questions static timing analysis plays major role in physical designpd flow. Unfortunately, there is no book currently ava able that can be used by a working engineer to get acquainted with the tails of static timing analysis. This way, one can do timing and functional analysis same time but separately. So, coming to the question what are some of the best resources to l. Static timing analysis electrical engineering digital. Static timing analysis what is the longest delay in my circuit.