
84
6329A–PMAAC–12-Aug-07
AT73C206
(The day digit is rounded up to the month digit when the count value returns to 1.)
Month digit:
Range is 1 to 12. The month digit is rounded up to the year digit when the count value
returns to 1.
Year digit:
Range is 00 to 99. Years 00, 04, 08, …, 92, 96 are leap years (corresponding to the year
2000 to 2099).
Rounding up from any incorrect and invalid data in the counter register results in unpredictable
behavior of the chip. Only valid and correct data must be written to the counter register.
6.8.1.8 RTCADJ: RTC Adjustment Register (Address 17h)
F6 ~ F0
The count value of one second is changed by the value of this register. Normally, the second
count is incremented by 32768 clock pulses generated by the oscillator. The clock error offset
circuit functions by writing data to this register.
Register value F6=“0”: The count value is incremented by ((F5,F4,F3,F2,F1,F0)-1) x 2.
Register value F6=“1”: The count value is decremented by((/F5,/F4,/F3,/F2,/F1,/F0)+1) x 2.
When F6,F5,F4,F3,F2,F1,F0= (*,0,0,0,0,0,*), there is no change in the count value.
/F5, /F4, /F3, /F2, /F1, /F0 indicate reversed F5, F4, F3, F2, F1, F0.
Example
When (F6,F5,F4,F3,F2,F1,F0)=(0,0,0,0,1,1,1) and second digit is 00, 20 or 40, the count value
becomes 32768+(7-1)Þ2=32780.It puts clock back.
When (F6,F5,F4,F3,F2,F1,F0)=(0,0,0,0,0,0,1) and second digit is 00, 20 or 40, count value is
hold at 32768 without making any change.
When 2 pulses are added to clock every 20sec, the count value becomes 2/(32768 x 20)=3.051
ppm and the clock will be put back around 3ppm. Likewise, when 2 pulses are reduced, 3ppm
will be put forward. The clock error can be regulated in maximum ±1.5ppm.
But the clock error offset corrects only clock not oscillator frequency. (32k clock output not
guaranteed.)
Bit7 6543210
Symbol Reserved F6 F5 F4 F3 F2 F1 F0
R/W --- R/W R/W R/W R/W R/W R/W R/W
Default --- --- --- --- --- --- --- ---