assert_never

Ensures that the value of a specified expression contains only 0 and 1 bits when a qualifying expression is TRUE.


	Parameters: severity_level width property_type msg coverage_level	Class: single-cycle assertion

Syntax

Parameters


	severity_level	Severity of the failure. Default: ‘OVL_ERROR.
	width	Width of the test_expr argument. Default: 1.
	property_type	Property type. Default: ‘OVL_ASSERT.
	msg	Error message printed when assertion fails. Default: “VIOLATION”.
	coverage_level	Coverage level. Default: ‘OVL_COVER_ALL.

Ports


clk		Clock event for the assertion. The checker samples on the rising edge of the clock.
reset_n		Active low synchronous reset signal indicating completed initialization.
qualifier		Expression that indicates whether or not to check test_expr .
test_expr	[ width - 1: 0 ]	Expression that should contain only 0 or 1 bits when qualifier is TRUE.

Description

The assert_never_unknown assertion checker checks the expression qualifier at each rising edge of clk to determine if it should check test_expr. If qualifier is sampled TRUE, the checker evaluates test_expr and if the value of test_expr contains a bit that is not 0 or 1, the assertion fails.

The checker is useful for ensuring certain data have only known values following a reset sequence. It also can be used to verify tristate input ports are driven and tristate output ports drive known values when necessary.

Assertion Checks


	test_expr contains X/Z value	The test_expr expression contained at least one bit that was not 0 or 1; qualifier was sampled TRUE; and ‘OVL_XCHECK_OFF is not set.

Cover Points


	qualifier	A never_unknown check was initiated.
	test_expr_change	Expression changed value.

Notes

1. If ‘OVL_XCHECK_OFF is set, all assert_never_unknown checkers are turned off.

assert_never_unknown #(
	‘OVL_ERROR, 8, ‘OVL_ASSERT, “Error: data unknown or undriven”, ‘OVL_COVER_ALL)		// severity_level // width // property_type // msg // coverage_level
	valid_data (
		clk, reset_n, rd_data, data);	// clock // reset // qualifier // test_expr

assert_never_unknown