APM: Difference between revisions

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=== Setting APM Driver Version ===

After an APM interface is connected, APM '''always''' runs as if it was version 1.0, to support legacy code. Unfortunately in that mode it isn't possible to do some things as setting the power state for all devices (as needed e.g. to shut the system down). So, if the APM installation check reports a version higher than 1.0, it might be useful to tell the APM that you support 1.1 or 1.2 version using INT 0x15 / AX=0x530E

<source lang="asm">

mov ah,53h ;this is an APM command

mov al,0eh ;set driver supported version command

mov bx,0000h ;device ID of system BIOS

mov ch,01h ;APM driver major version

mov cl,01h ;APM driver minor version (can be 01h or 02h if the latter one is supported)

int 15h

jc .version_error

;at this point AX holds the APM version that is connected, AH=major version AL=minor version

;so an additional check might be implemented

jmp .no_error

.version_error:

;ah can hold: 03h if the interface wasn't connected, 09h if the device ID wasn't recognised (BX nonzero), 0Bh if APM v1.1 still isn't engaged

.no_error:

;continue