3-WIRE REAL-TIME CLOCK
S-35190A
Rev.2.4_00
3. How to confirm setting value for register and result of correction
The S-35190A does not adjust the frequency of the crystal oscillation by using the clock-correction function. Therefore
users cannot confirm if it is corrected or not by measuring output 32.768 kHz. When the function to 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 33.
INT pin
(1 Hz output)
a
a
b
a
a
Once
19 times or 59 times
B0 = 0, a : 19 times, b : Once
B0 = 1, a : 59 times, b : Once
Figure 33 Confirmation of Correction Result
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
Before correction 00 h (Tave = a)
Average frequency [Hz] Per Day [s]
1.000080
86393
86399.9
After correction
66 h (Tave = (a × 19 + b) ÷ 20) 1.00000065
Calculating the average frequency allows to confirm the result of correction.
*1. Use a high-accuracy frequency counter of 7 digits or more.
Caution Measure the oscillation frequency under the usage conditions.
Seiko Instruments Inc.
29
SII [ SEIKO INSTRUMENTS INC ]
