Category: BIOS
INT 1A - TIME - GET REAL-TIME CLOCK TIME (AT,XT286,PS) AH = 02h CF clear to avoid bug (see below) Return: CF clear if successful CH = hour (BCD) CL = minutes (BCD) DH = seconds (BCD) DL = daylight savings flag (00h standard time, 01h daylight time) CF set on error (i.e. clock not running or in middle of update) Notes: this function is also supported by the Sperry PC, which predates the IBM AT; the data is returned in binary rather than BCD on the Sperry, and DL is always 00h MS-DOS/PC DOS IO.SYS/IBMBIO.COM use this function to detect if a RTC is preset by checking if the returned values are non-zero. If they are, this function is called one more time, before it is assumed that no RTC is present. BUG: some BIOSes leave CF unchanged if successful, so CF should be cleared before calling this function SeeAlso: AH=00h,AH=03h,AH=04h,INT 21/AH=2Ch