assert_window

Ensures that the value of a specified expression is TRUE in a specified window between a start event and an end event.


	Parameters: severity_level property_type msg coverage_level	Class: event-bounded assertion

Syntax

Parameters


	severity_level	Severity of the failure. Default: ‘OVL_ERROR.
	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.
	start_event		Expression that opens an event window.
	test_expr		Expression that should be TRUE in the event window
	end_event		Expression that closes an event window.

Description

The assert_window assertion checker checks the expression start_event at each rising edge of clk to determine if it should open an event window at the start of the next cycle. If start_event is sampled TRUE, at each subsequent rising edge of clk, the checker evaluates end_event and test_expr. If a sampled value of test_expr is not TRUE, then the assertion fails. If end_event is TRUE, the checker closes the event window and returns to the state of monitoring start_event at the next rising edge of clk.

The checker is useful for ensuring proper changes in structures after various events. For example, it can be used to check that multiple-cycle operations with enabling conditions function properly with the same data. It can be used to check that single-cycle operations function correctly with data loaded at different cycles. It also can be used to verify synchronizing conditions that require date to be stable after an initial triggering event.

Assertion Check


	ASSERT_WINDOW	The test_expr expression changed value during an open event window.

Cover Points


	window_open	A change check was initiated.
	window_close	A change check lasted the full num_cks cycles.

assert_window #(
	‘OVL_ERROR, ‘OVL_ASSERT, “Error: write without grant”, ‘OVL_COVER_ALL)		// severity_level // property_type // msg // coverage_level
	valid_sync_data_bus_write (
		clk, reset_n, write, bus_gnt, write_ack );	// clock // reset // start_event // test_expr // end_event