A WAIT statement suspends subprogram execution until a signal changes, a condition becomes TRUE, or a defined time period has elapsed. You cam also use combinations of these.

WAIT [ON sensitivity_list] [UNTIL condition] [FOR time_expression];

sensititvity_list

List of signals which can cause an event.

condition

Specifies an expression which evaluates to a BOOLEAN value (TRUE or FALSE).

time_expression

Specifies a time expression which evaluates to a TIME value.

WAIT ON INPUT;

WAIT UNTIL ctrl > 1.5;

WAIT FOR TDELAY*unit_time;