Data Sheet

SD2405ALPI IIC 串行接口的实时时钟IC
!
frequency(HZ)
FS3
FS2
FS1
FS0
0
0
0
0
0
32768
0
0
0
1
4096
0
0
1
0
1024
0
0
1
1
64
0
1
0
0
32
0
1
0
1
16
0
1
1
0
8
0
1
1
1
4
1
0
0
0
2
1
0
0
1
1
1
0
1
0
1/2
1
0
1
1
1/4
1
1
0
0
1/8
1
1
0
1
1/16
1
1
1
0
1S
1
1
1
1
(3) Countdown timer interrupt
The countdown timer interrupt is enabled and disabled via the timer control register bit
INTDE.The frequency source is selected by the TDS1, TDS0 bits in the control register
3(CTR3).
TDS1
TDS0
Source clock(HZ)
0
0
4096
0
1
64
1
0
1
1
1
1/60
When countdown timer interrupt is enabled and an 8-bit binary countdown data is
written into the countdown timer, the countdown timer will reduce according to the source
clock. If the countdown timer reduce to zero, The countdown interrupt flag will be set
(control register 1 bit INTDF) to “1” immediately . The longest period of the countdown timer
interrupt is 256 minutes.
5.4 Time Trimming Register [12h]
For the following reasons:
1) In general crystal oscillators are classified by their central frequency of CL
(load capacitance) and available further grouped in several ranks as ±10 ，
±20 and ±50ppm of fluctuations in precision.
2) The fluctuation of IC circuit frequency is ±5~10ppm at room temperature.