17. Digital offset function
RX8130CE
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ETM50E-07
Seiko Epson Corporation
52
How to calculate the offset value
1 ) When the offset value is positive:
L [7
1] =[Offset Value]/ 3.05 However, decimals are discarded.
Example calculation: When the offset value is +192
10
-6
L[7
1] = 192.26 / 3.05 = 63 (Dec)
= 0111111(bin) is set.
2 ) When the offset value is negative:
L[7
1] = 128
– [Offset Value] / 3.05 However, decimals are discarded.
Example calculation: When the offset value is
158
10
-6
L[7
1] = 128 - ( 158 / 3.05 ) = 76(Dec) = 1001100(bin) is set.
3 ) When calculate from accuracy of a clock
To adjust 30 seconds in 30 days:
Example calculation: 30sec. / 2592000s (30days) = 11.57
10
-6
Positive offset
L[7
1] = 11.57 / 3.05 = 4 (Dec) However, decimals are discarded.
= 0000100(bin) is set.
Negative offset
L[7
1] = 128
– ( 11.57 / 3.05 ) = 124 (Dec) However, decimals are discarded.
= 1111100(bin) is set.
17.2. Effect of the digital offset function to other functions
Because this function adjusts an internal sub-second clock, this function affects the a Wakeup timer interrupt
function and FOUT function
1) FOUT function
1 Hz setting: Once in 10 seconds, the 1 Hz period fluctuates.
1024 Hz setting: Once in 10 seconds, the 1024 Hz period fluctuates.
There are cases where there is no fluctuation, depending on the offset correction value.
32.768 kHz
Not affected.
2) Wakeup timer interrupt function
64 Hz or 1 Hz source clock setting:
Once in 10 seconds, the period fluctuates.
When the timer intervals are long, the fluctuations appear small.
4096
Hz source clock setting:
N
ot affected.
