Int 15H [AT] [PS/2] Function 91H (145) Device post

Invoked by the ROM BIOS fixed disk, floppy disk, network, and keyboard drivers to signal that I/O is complete and/or the device is ready.

Call with:

AH = 91H

AL = device type

00H—7FH serially reusable devices

80H—BFH reentrant devices

ES:BX = segment:offset of request block for device types 80H—BFH

Returns:

AH = 00H

Notes:

Predefined device types that may use Device Post are:

00H disk (may time-out) 01H floppy disk (may time-out) 02H keyboard (no time-out) 03H pointing device (PS/2, may time-out) 80H network (no time-out)

The ROM BIOS printer routine does not invoke this function because printer output is not interrupt driven.

A multitasking program manager would be expected to capture Int 15H Function 91H so that it can be notified when I/O is completed and awaken the requesting task. The default BIOS routine for this function simply returns with the carry flag clear and AH = 00H.