INT 15,90 - Device Busy

AH = 90h

AL = type code:

= 00 disk

= 01 diskette

= 02 keyboard

= 03 pointing device

= 80 network (ES:BX = NCB)

= FC fixed disk reset (PS/2)

= FD diskette motor start

= FE printer

ES:BX = pointer to network control block if waiting for network

on return:

CF = 0 if wait not satisfied

= 1 if wait time satisfied

AH = when CF set, 80h for PC & PCjr, 86h for XT (BIOS 11/8/82)

- tells the OS a a program is about to wait for a device

- used for multitasking OS development