INT 1A,6 - Set Real Time Clock Alarm (XT 286,AT,PS/2)

AH = 06

CH = hours in BCD

CL = minutes in BCD

DH = seconds in BCD

on return:

CF = 1 if alarm already set or clock inoperable

- alarm setting is not relative like some sources claim, but the

actually clock time the interrupt should occur

- settings values must be in BCD

- when the alarm time is reached ~INT 4A~ is executed

- INT 4A vector should be replaced with address of the alarm

handling interrupt routine before setting the alarm

- ~INT 1A,7~ should be called to disable the ~RTC~ alarm