assert_always_on

Ensures that the value of a specified expression is TRUE when a sampling event undergoes a specified transition.


	Parameters: severity_level edge_type property_type msg coverage_level	Class: 2-cycle assertion

Syntax

Parameters


	severity_level	Severity of the failure. Default: ‘OVL_ERROR.
	edge_type	Transition type for sampling event: ‘OVL_NOEDGE, ‘OVL_POSEDGE, ‘OVL_NEGEDGE or ‘OVL_ANYEDGE. Default: ‘OVL_NOEDGE.
	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.
	sampling_event		Expression that (along with edge_type) identifies when to evaluate and test test_expr.
	test_expr		Expression that should evaluate to TRUE on the rising clock edge.

Description

The assert_always_on_edge assertion checker checks the single-bit expression sampling_event for a particular type of transition. If the specified transition of the sampling event occurs, the single-bit expression test_expr is evaluated at the rising edge of clk to verify the expression does not evaluate to FALSE.

The edge_type parameter determines which type of transition of sampling_event initiates the check:

‘OVL_POSEDGE performs the check if sampling_event transitions from FALSE to TRUE.

‘OVL_NEGEDGE performs the check if sampling_event transitions from TRUE to FALSE.

‘OVL_ANYEDGE performs the check if sampling_event transitions from TRUE to FALSE or from FALSE to TRUE.

‘OVL_NOEDGE always initiates the check. This is the default value of edge_type. In this case, sampling_event is never sampled and the checker has the same functionality as assert_always.

The checker is a variant of assert_always, with the added capability of qualifying the assertion with a sampling event transition. This checker is useful when events are identified by their transition in addition to their logical state.

Assertion Check


	ASSERT_ALWAYS_ON_EDGE	Expression evaluated to FALSE when the sampling event transitioned as specified by edge_type.

Cover Points

See also

Examples


assert_always_on_edge #(
	‘OVL_ERROR, ‘OVL_POSEDGE, ‘OVL_ASSERT, “Error: new req when FSM not ready”, ‘OVL_COVER_ALL)		// severity_level // edge_type // property_type // msg // coverage_level
	request_when_FSM_idle (
		clk, reset_n, req, state == ‘IDLE);	// clock // reset // sampling_event // test_expr

Ensures that (state == ‘IDLE) is TRUE at each rising edge of clk when req transitions from FALSE to TRUE.


assert_always_on_edge #(
	‘OVL_ERROR, ‘OVL_ANYEDGE, ‘OVL_ASSERT, “Error: req transition when FSM not idle”, ‘OVL_COVER_ALL)		// severity_level // edge_type // property_type // msg // coverage_level
	req_transition_when_FSM_idle (
		clk, reset_n, req, state == ‘IDLE);	// clock // reset // sampling_event // test_expr

Ensures that (state == ‘IDLE) is TRUE at each rising edge of clk when req transitions from TRUE to FALSE or from FALSE to TRUE.


assert_always_on_edge #(
	‘OVL_ERROR, ‘OVL_NOEDGE, ‘OVL_ASSERT, “Error: req when FSM not idle”, ‘OVL_COVER_ALL)		// severity_level // edge_type // property_type // msg // coverage_level
	req_when_FSM_idle (
		clk, reset_n, 1’b0, !req \|\| (state == ‘IDLE) );	// clock // reset // sampling_event // test_expr

Ensures that (!req || (state == ‘IDLE)) is TRUE at each rising edge of clk.