S35390A datasheet(29/51 Pages) SII

29 / 51 page

FOR AUTOMOTIVE 105°C OPERATION 2-WIRE REAL-TIME CLOCK

Rev.2.2_00

S-35390A H Series

Seiko Instruments Inc.

3. How to confirm setting value for register and result of correction

The S-35390A H Series does not adjust the frequency of the crystal oscillation by using the function of clock correction.

Therefore users cannot confirm if it is corrected or not by measuring output 32.768 kHz. When the function of clock

correction is being used, the cycle of 1 Hz clock pulse output from the

INT

pin changes once in 20 times or 60 times,

as shown in Figure 31.

INT1 pin

(1 Hz output)

In case of B0 = 0: a = 19 times, b = Once

In case of B0 = 1: a = 59 times, b = Once

19 times or 59 times

Once

Figure 31 Confirmation of Clock Correction

Measure a and b by using the frequency counter

*1. Calculate the average frequency (Tave) based on the measurement

results.

B0 = 0, Tave = (a

× 19 + b) ÷ 20

B0 = 1, Tave = (a

× 59 + b) ÷ 60

Calculate the error of the clock based on the average frequency (Tave). The following shows an example for

confirmation.

Confirmation example: When B0 = 0, 66h is set

Measurement results: a = 1.000080 Hz, b = 0.998493 Hz

Clock Correction Register Setting Value

Average Frequency [Hz]

Per Day [s]

Before correction

00 h (Tave = a)

1.000080

86393

After correction

66 h (Tave = (a

× 19 + b) ÷ 20) 1.00000065

86399.9

Calculating the average frequency allows to confirm the result of correction.

*1.

Use a frequency counter with 7-digit or greater precision.

Caution

Measure the oscillation frequency under the usage conditions.

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