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2015-12-0001

PT0280-8

12/11/15

26

PT7C43390/43390C

Real-time Clock Module

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.