This diversity is useful because it allows for comparative studies that can identify the main types of selective pressures driving the evolution of complex forms of communication. Vocal complexity is typically defined as the number of different vocalizations a species can make, or vocal repertoire size and this trait differs extensively across taxa 6, 7, 8. In particular, there is tremendous interest in documenting the diversity of ‘vocal complexity’ in animals 5. Despite this uniqueness, several aspects of language can be studied comparatively 3, 4. The keyword “not” is used to specify that the property should never be true.Human’s ability to combine sounds together into an endless array of meaningful words and sentences is unique, making the evolutionary roots of language a focus of intense interest 1, 2. a_3: assert clk) p) //Not allowedīelow sequence checks that if signal “a” is high on a given positive edge of the clock, then after 2 clock cycles, signal “b” shall not be high. sequence seq Ĭalling a property with a clock definition from within the assert statement is not allowed. If the property is true, the assertion fails. we expect the property to be false always. In all the examples shown so far, the property is checking for a true condition. the expression to be checked can be called from the assert statement directly as shown below. Forbidding a propertyĪ separate property definition is not needed to assert a sequence. This will help increase the re-use of the basic sequence definitions. In general, it is a good idea to define the clocks in property definitions and keep the sequences independent of the clocks. sequence clk) a #2 b Įndsequence Clock defined in the property definition sequence seq The previous example shows the usage of a clock inside the sequence definition. Clock usage in SVAĪ clock can be specified in a sequence, in a property or even in an assert statement. Note:: sequence begins when signal “a” is high on a positive edge of the clock. If signal “b” is not asserted after 2 clock cycles, the assertion fails. If signal “a” is high on any given positive edge of the clock, the signal “b” should be high 2 clock cycles after that. If the signal “a” is not high, then the sequence fails. For example, #2 means 2 clock cycles.īelow sequence checks for the signal “a” being high on a given positive edge of the clock. In SVA, clock cycle delays are represented by a “#” sign. This seq can be used as, sequence s_lib_instĮndsequence Sequences with timing relationship sequence clk) a || b īy defining arguments in a sequence definition, the same sequence can be re-used for similar behavior.įor example, we can define a sequence as below. If both the signals are low, the assertion will fail. sequence clk) a=1 Ĭlick to execute on SystemVerilog assertion sequence A sequence with a logical relationshipīelow sequence, seq_2 checks that on every positive edge of the clock, either signal “a” or signal “b” is high. If the signal “a” is not high on any positive clock edge, the assertion will fail. In the below example the sequence seq_1 checks that the signal “a” is high on every positive edge of the clock. SVA provides a keyword to represent these events called “sequence”. Clock defined in the property definitionīoolean expression events that evaluate over a period of time involving single/multiple clock cycles.Clock defined in the sequence definition.
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