Reads the current time from the CMOS time/date chip.
Call with:
AH = 02H
Returns:
CH = hours in binary coded decimal (BCD)
CL = minutes in BCD
DH = seconds in BCD
DL = daylight-saving-time code
00H if standard time
01H if daylight saving time
and, if clock running
Carry flag = clear
or, if clock stopped
Carry flag = set