INT 1aH 06H: Set Real-Time Clock Alarm

 Expects: AH    06H
          CH    hours, in BCD
          CL    minutes, in BCD
          DH    seconds, in BCD
 Returns: AH    0
          CF    NC (0) no error
                CY (1) alarm already operating
    Info: Sets the BIOS to invoke INT 4aH at the specified time.

          You must supply an INT 4aH handler if you want to get control at
          the specified time (and avoid a system crash!).  The vector for
          INT 4aH is at 0000:0128H.

          Only one alarm may be set at a time.  If an alarm is already
          active, this returns with the Carry Flag set and take no action.

          Use INT 1aH 07H to cancel a previously-set alarm.

    Note: Using this as described is quite unusual.  A more common
          technique is to patch a TSR into INT 08H and keep an eye on the
          system time.  That way you can set up multiple timers, etc.

See Also: INT 1aH (BIOS Time I/O)
          ROM-BIOS Functions