
3-WIRE REAL-TIME CLOCK
S-35190A
Rev.1.2_00
Seiko Instruments Inc.
24
Clock Adjustment Function
A clock adjustment function is provided to logically perform slow/fast adjustment of the 32 kHz clock and
correct a slow/fast clock with high accuracy. Use the clock adjustment register to set this function. When not
using this function, be sure to set it to 00h.
The clock adjustment register value is calculated by the following expression.
(1) If current oscillation frequency > target frequency (in case the clock is fast)
Register value
*1 = 128 Integral value
(
Minimum resolution
*4)
(Current oscillation frequency
actual measurement value
*2) (Target oscillation frequency
*3)
×
(Current oscillation frequency
actual measurement value
*2)
Caution The figure range which can be corrected is that the calculated value is from 0 to 64.
*1. The register value is the value set to the clock adjustment register. Set the binarized value of
this value to the clock adjustment register.
*2. This is the measurement value of the signal that is output to the INT pin when 1 Hz clock
output setting is made (32kE
= 0, INT1ME = 0, INT1FE = 1, INT1 register_1 is 01h).
*3. This is the frequency to be adjusted by using the clock adjustment function.
*4. For the minimum resolution, 3.052 ppm or 1.017 ppm can be set using B7 of the clock
adjustment register. When B7 is 0, 3.052 ppm is set and logical slow/fast adjustment is
performed every 20 seconds. When B7 is 1, 1.017 ppm is set and logical slow/fast
adjustment is performed every 60 seconds.
Table 12
B7
= 0
B7
= 1
Slow/fast adjustment
Every 20 seconds
Every 60 seconds
Minimum resolution
3.052 ppm
1.017 ppm
Correction range
195.3 ppm to +192.2 ppm
65.1 ppm to +64.1 ppm
The example of calculated value 1
Current oscillation frequency actual measurement value = 1.000080 [Hz],
Target oscillation frequency
= 1.000000 [Hz],
B7
= 0 (minimum resolution = 3.052 ppm),
Register value
= 128 Integral value
(1.000080)
× (3.052 × 106)
(1.000080)
(1. 000000)
= 128 Integral value (26.21) = 128 = 26 = 102
Thus, set up (B7,B6,B5,B4,B3,B2,B1,B0) = (0,1,1,0,0,1,1,0) for the clock adjustment register.