INT 1Ah,  08h (8)        Set Clock-Activated Power-On Mode        Convertible

Sets the time at which the computer will automatically power on.

On entry:      AH         08h
CH         Hours (BCD)
CL         Minutes (BCD)
DH         Seconds (BCD)

Returns:       CF         Set if clock not operating or alarm already
set; else cleared


Notes:         This service is available only for the PC
Convertible. Previous machines will report
unpredictable results (including the state of the
Carry Flag). ATs, XT-286s, and the PS/2 family will
set the Carry Flag, thus reporting an error state.

All dates are in Binary Coded Decimal (BCD). For
example, June 1, 1985 will be set as CX = 1985; DX =

The real-time clock is the clock that runs even when
the computer is turned off. A CMOS battery is used
so that, even while the computer is off, the date,
time, and alarm time are maintained.

After this service is executed, the machine will
automatically power on as soon as the hour, minute,
and second specified match the time on the real-time
clock date. If the system is already on, then INT
4Ah (User Alarm) will be executed.

If the system is on, the alarm interrupt (INT 4Ah)
will continue to occur every 24 hours at the
specified time until it is reset via Service 07h
(Reset Real-Time Clock Alarm). Only one alarm time
can be active at a time.

See also: INT 1Ah, 06h
See also: INT 1Ah, 07h
See also: INT 1Ah, 09h
See also: INT 4Ah

INT 1Ah, 08h (8) Set Clock-Activated Power-On Mode Convertible