Description
For AHDL If Then or Case Statements, a non-specified value will default to a logic zero. For example:
IF (a) THEN
b = c;
END IF;
When a is high, b gets the value of c, otherwise, when a is low, b will be a logic zero.
You can use a Default section directly after the BEGIN statement in the AHDL file to make the default value high. For example:
BEGIN DEFAULTS
a = VCC;
END DEFAULTS;
When using a Case Statement to define a state machine, a non-specified value will default to the current state.