SYSTEM VERILOG SIMULATION SOFTWARE FROM MENTOR

('Is it working correctly?') They may also be used to provide functional coverage information for a design ('How good is the test?'). As one of the 'big 3' simulators, VCS is qualified for ASIC (validation) sign-off at nearly all semiconductor fabs.Assertions are primarily used to validate the behavior of a design. SystemVerilog Assertions (SVA) form an important subset of SystemVerilog, and as such may be introduced into existing Verilog and VHDL design flows.1) Verilog simulation: wall clock time 2) Verilog simulation: timing within the simulation a) These delays are set by delays discussed in the following slides 3) Circuit delays (in circuits created by the synthesizer tool + theDue to a strategic decision to support SystemVerilog (instead of SystemC), and the timely acquisition of Superlog (the forerunner to SystemVerilog), Synopsys/VCS was the first SystemVerilog simulator in the market. Introduction SystemVerilog is a set of extensions to the Verilog hardware description language and is expected to become IEEE standard 1800 later in 2005. This post described three different Verilog and SystemVerilog constructs that can cause simulation and synthesis mismatch due to Verilog X optimism.By Michael Smith, Doulos Ltd. But in simulation, the simulator will behave as though a positive edge on the clock has occurred, latching data into any registers triggered by posedge.

System Verilog Simulation Software From Mentor

ProgrammingSimulation paired with co-emulation will deliver dramatic speedup of execution of verification. Refer to 'Timing Simulation' on page 10 and the documentation included with your simulation tool for information about performing timing simulation. Timing simulation requires information extracted from software, which overrides default unit delays in the Verilog libraries. 1 Environment Setup and starting ModelSim The.Perform a timing simulation of your design after place-and-route. Assertions may also be used as a formal specification language, making the requirements clear and unambiguous, and making it possible to automate validation of the design against the specification.Ajith S Ramani and Abdelrahman 10/2016 ModelSim is an HDL simulation software from Mentor Graphics.

Coverage statements ( cover property) are concurrent and have the same syntax as concurrent assertions, as do assume property statements, which are primarily used by formal tools. Alternatively, you can use the translate_off/translate_on pragmas.In SystemVerilog there are two kinds of assertion: immediate ( assert) and concurrent ( assert property). They are understood by Design Compiler, which knows to ignore them with a warning. Properties can be checked dynamically by simulators such as VCS, or statically by a separate property checker tool ' such as Magellan.

An assertion is basically a statement that something must be true, similar to the if statement. Behavior over time, as defined by one or more clocks.Immediate Assertions Immediate assertions are procedural statements and are mainly used in simulation. The three types of concurrent assertion statement and the expect statement make use of sequences that describe the design's temporal behavior ' i.e.

They can be used, for example, to write out a message, set an error flag, increment a count of errors, or signal a failure to another part of the testbench.AeqB: assert (a = b) else begin error_count++ $error('A should equal B') endConcurrent Assertions The behavior of a design may be specified using statements similar to these:'The Read and Write signals should never be asserted together.''A Request should be followed by an Acknowledge occurring no more than two clocks after the Request is asserted.'Concurrent assertions are used to check behavior such as this. In addition, the system task $info indicates that the assertion failure carries no specific severity.ReadCheck: assert (data = correct_data) else $error('memory read error') Igt10: assert (I > 10) else $warning('I has exceeded 10') The pass and fail statements can be any legal SystemVerilog procedural statement. There are three severity system tasks that can be included in the fail statement to specify the severity level: $fatal, $error (the default severity) and $warning. A equals B') else $error('It's gone wrong') You may omit the pass statement yet still include a fail statement:Assert (A = B) else $error('It's gone wrong') The failure of an assertion has a severity associated with it.

A concurrent assertion in an initial block is only tested on the first clock tick.)The first assertion example above does not contain a clock. (Concurrent assertions may also be used as statements in initial or always blocks. They usually appear outside any initial or always blocks in modules, interfaces and programs. |-> is the implication operator, so this assertion checks that whenever Req is asserted, Ack must be asserted on the next clock, or the following clock.Concurrent assertions like these are checked throughout simulation. For example,Assert property ( Clock) Req |-> # Ack) Where Req is a simple sequence (it's just a boolean expression) and # Ack is a more complex sequence expression, meaning that Ack is true on the next clock, or on the one following (or both). For example,Asserts that the expression Read & Write is never true at any point during simulation.Properties are often built using sequences.

If there is a match, for each successful match of the antecedent sequence expression, the consequent sequence expression is separately evaluated, beginning at the end point of the match.For overlapped implication, if there is a match for the antecedent sequence expression, then the first element of the consequent sequence expression is evaluated on the same clock tick.In the example above, if the sequence s1 matches, then sequence s2 must also match. The left-hand side operand of the implication is called the antecedent sequence expression, while the right-hand side is called the consequent sequence expression.If there is no match of the antecedent sequence expression, implication succeeds vacuously by returning true. Attach a precondition to a sequence and evaluate the sequence only if the condition is successful. The second assertion is only checked when a rising clock edge has occurred the values of Req and Ack are sampled on the rising edge of Clock.Implication The implication construct ( |->) allows a user to monitor sequences based on satisfying some criteria, e.g.

This model of execution corresponds to the way a RTL description of a design is interpreted after synthesis.A clock tick is an atomic moment in time and a clock ticks only once at any simulation time. Everything in between clock ticks is ignored. In fact, the values of the variables in the property are sampled right at the end of the previous time step. Sequences, too, may be declared separately:Sequence request Req endsequence sequence acknowledge # Ack endsequenceProperty handshake Clock) request |-> acknowledge endpropertyAssertion Clocking Concurrent assertions ( assert property and cover property statements) use a generalized model of a clock and are only evaluated when a clock tick occurs. Properties may also be declared separately, for example:Property not_read_and_write ! (Read & Write) endproperty assert property (not_read_and_write) Complex properties are often built using sequences.

The clock is explicitly specified in the concurrent assertion: assert property clk) a #1 b) The clock is explicitly specified in the property: property p clk) a #1 b endproperty assert property (p) When monitoring asynchronous signals, a simulation time step corresponds to a clock tick.The clock for a property can be specified in several ways, of which the most common are: ( clk & GatingSig)) or other more complex expression.

The sequence is true over time if the boolean expressions are true at the specific clock ticks. Otherwise, the sequence (b #1 c) must never evaluate to true.Sequences A sequence is a list of boolean expressions in a linear order of increasing time. So, this assertion means that if Reset becomes true at any time during the evaluation of the sequence, then the attempt for p1 is a success.

The # operator delays execution by the specified number of clocking events, or clock cycles.