INT 15H 90H: Device Busy

 Expects: AH    90H
          AL    device type:  00H fixed disk time-out
                              01H diskette time-out
                              02H keyboard
                              03H pointed device time-out
                              21H waiting for keyboard input
                              80H network
                              fcH fixed-disk reset time-out
                              fdH diskette drive motor start
                              feH pointing device time-out
          ES:BX addr of network control block (if AL = 80H or higher)
          CF    must be NC (0) before calling
 Returns: AH    00h wait time not satisfied
          CF    NC (0) wait time not satisfied; use your own wait rtn
                CY (1) minimum wait time satisfied (wait performed)
    Info: This service is designed to be intercepted by a multitasking
          operating system.  It could be used by BIOS disk handlers or
          other hardware to perform programmed wait-for-I/O-completion,
          which would allow other tasks to be dispatched while I/O is in

          When unintercepted, the BIOS simply sets AH to 0 and clears CF.

See Also: INT 15H (extended AT services)
          BIOS Data Area
          ROM-BIOS Functions