PCF2123U/10AA/1 View Datasheet(PDF) - NXP Semiconductors.
Part Name
Description
MFG CO.
'PCF2123U/10AA/1' PDF : 64 Pages View PDF
NXP Semiconductors
PCF2123
SPI Real time clock/calendar
8.9 Offset register
The PCF2123 incorporates an offset register (address 0Dh) which can be used to
implement several functions, such as:
• Ageing adjustment
• Temperature compensation
• Accuracy tuning
The offset is made once every two hours in the normal mode, or once every hour in the
course mode. Each LSB will introduce an offset of 2.17 ppm for normal mode and
4.34 ppm for course mode. The values of 2.17 ppm and 4.34 ppm are based on a nominal
32.768 kHz clock. The offset value is coded in two’s complement giving a range of
+63 LSB to 64 LSB.
Table 37. Register Offset_register
OFFSET[6:0]
Offset value in
decimal
0 1 1 1 1 1 1 +63
0 1 1 1 1 1 0 +62
:
:
0 0 0 0 0 1 0 +2
0 0 0 0 0 0 1 +1
0 0 0 0 0 0 0 0[1]
1 1 1 1 1 1 1 1
1 1 1 1 1 1 0 2
:
:
1 0 0 0 0 0 1 63
1 0 0 0 0 0 0 64
[1] Default mode.
Offset value in ppm
Normal mode
MODE = 0
+136.71
+134.54
:
+4.34
+2.17
0
2.17
4.34
:
136.71
138.88
Course mode
MODE = 1
+273.42
+269.08
:
+8.68
+4.34
0
4.34
8.68
:
273.42
277.76
The correction is made by adding or subtracting 64 Hz clock correction pulses, thereby
changing the period of a single second.
Table 38. Example of converting the offset in ppm to seconds
Offset in ppm Seconds per
Day
Week
Month
2.17
0.187
1.31
5.69
4.34
0.375
2.62
11.4
Year
68.2
136
In normal mode, the correction is triggered once per two hours and then correction pulses
are applied once per minute until the programmed correction values have been
implement.
In course mode, the correction is triggered once per hour and then correction pulses are
applied once per minute up to a maximum of 60 minutes. When correction values greater
than 60 are used, additional correction pulses are made in the 59th minute (see Table 39).
PCF2123
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 6 — 15 July 2013
© NXP B.V. 2013. All rights reserved.
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