SECTION 6
Conversions and Interfaces
6-116 PEN*KEY
R
6200/6300 Hand-Held Computer Programmer’s Reference Guide
INT 1Ah, Function AH = 06h: Set Real-Time Clock Alarm
BIOS
If alarm currently enabled, function is not performed. Writes alarm hour,
minute, and second data to CMOS RAM area of MC 146818 and sets AIE bit in
Register B.
Must wait for updateĆinĆprogress bit to become 0 and disable interrupts before
accessing CMOS data. Once activated, alarm expires once every 24 hours until
deactivated. When alarm expires, INT 4Ah is issued.
If calling program needs control passed to it, it must place interrupt handler
address in vector for INT 4Ah. User routine must save and restore all registers
and preserve machine state.
If hour high two bits set, alarm expires every hour. If minutes high two bits set,
alarm expires every minute. If seconds high two bits set, alarm expires every
second.
On Entry:
AH = 06h
CH = Hours in BCD (0ć23)
CL = Minutes in BCD (0ć59)
DH = Seconds in BCD (0ć59)
On Return:
If successful:
Carry = 0
If NOT successful:
Carry = 1
INT 1Ah, Function Ah = 07h: Reset the Real-Time Clock Alarm
BIOS
Clears any pending alarm specified by INT 1Ah, Function 06h by resetting the
AIE bit in Register B.
On Entry:
AH = 07h
On Return:
None
6. Conversions and
Interfaces
