Immediate assertions are typically used to verify that expressions are within their required bounds, such as no overreach of the value of a counter or an illegal condition such a write without an enable. The action block is typically used for debug to display more information as to the cause of the error. However, immediate assertions can also be used to modify testbench variables for use in monitors or in other assertions, or to change the course of a testbench flow. This article explains the immediate assertion modes, their restrictions, and it provides guidelines into their uses.
IMMEDIATE ASSERTIONS AND SCHEDULED REGIONS
1800:4.4 Stratified event schedulerdefines the regions within a time slot. The figure below is a