PT7C43190 Datasheet, PDF (24/32 Pages) Pericom Semiconductor Corporation – Real-time Clock Module

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10.2. How to calculate
a. If current oscillation frequency > target frequency (in case the clock is fast)
Caution The figure range which can be corrected is that the calculated value is from 0 to 64.
*1. Convert this value to be set in the clock correction register. For how to convert, refer to "Calculation example 1".
*2. Measurement value when 1 Hz clock pulse is output from the INT pin.
*3. Target value of average frequency when the clock correction function is used.
*4. Refer to "Function to Clock Correction".
 Calculation example 1
In case of current oscillation frequency actual measurement value = 1.000070 [Hz], target oscillation frequency = 1.000000 [Hz],
B0 = 0 (Minimum resolution = 3.052 ppm)
Convert the correction value "106" to 7-bit binary and obtain "1101010b".
Reverse the correction value "1101010b" and set it to B7 to B1 of the clock correction register.
Thus, set the clock correction register:
(B7, B6, B5, B4, B3, B2, B1, B0) = (0, 1, 0, 1, 0, 1, 1, 0)
b. If current oscillation frequency < target frequency (in case the clock is fast)
Caution The figure range which can be corrected is that the calculated value is from 0 to 62.
 Calculation example 2
In case of current oscillation frequency actual measurement value = 0.999920 [Hz], target oscillation frequency = 1.000000 [Hz].
B0 = 0 (Minimum resolution = 3.052 ppm)
Thus, set the clock correction register:
(B7, B6, B5, B4, B3, B2, B1, B0) = (1, 1, 0, 1, 1, 0, 0, 0)
 Calculation example 3
In case of current oscillation frequency actual measurement value = 0.999920 [Hz], target oscillation frequency = 1.000000 [Hz],
B0 = 1 (Minimum resolution = 1.017 ppm)
This calculated value exceeds the correctable range 0 to 62.
B0 = "1" (minimum resolution = 1.017 ppm) indicates the correction is impossible.
2015-09-0015
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PT0274-7 10/16/15