WAIT Command

The WAIT command should be used to wait on vertical retrace or to wait on 
a desired status. The command allows for a time-out in milliseconds. The 
condition for wait has been met if port value ANDed with andmask has the 
waitonvalue. Register r0 is set to convey the status: 

   *  TRUE (1) means that the waiting condition has been met. 
   *  FALSE means that a time-out has occurred. 
 

 The wait is interruptable. This command should not be used in Cleanup 
 sections. 

 The port can be an immediate value, which presumes that the port is an 
 I/O port or a declared port. In these cases, the port's declaration type 
 is used in interpreting this command. 

 
 WAIT( port, andmask, timeout, waitonvalue );
 <andmask>  ::= <number>
 <timeout>  ::= <number>
 <waitonvalue> ::= <number>
 
 <port>  ::= <  constant>  |  <pio variable>  |  <mmio variable>