PCF2123U/5GA/1 View Datasheet(PDF) - NXP Semiconductors.
Part Name
Description
MFG CO.
'PCF2123U/5GA/1' PDF : 63 Pages View PDF
NXP Semiconductors
PCF2123
SPI Real time clock/calendar
Table 40. Effect of correction pulses
Frequency (Hz)
CLKOUT
32768
16384
8192
4096
2048
1024
1
Time source clock
4096
64
1
1⁄60
Effect of correction
no effect
no effect
no effect
no effect
no effect
no effect
affected
no effect
no effect
affected
affected
8.9.1 Offset calibration workflow
The calibration offset has to be calculated based on the time. Figure 20 shows the
workflow how the offset register values can be calculated:
Measure the frequency on pin CLKOUT:
fmeas
PCF2123
Product data sheet
Convert to time:
tmeas = 1 / fmeas
Calculate the difference to the ideal
period of 1 / 32768.00:
Dmeas = 1 / 32768 - tmeas
Calculate the ppm deviation compared
to the measured value:
Eppm = 1000000 × Dmeas / tmeas
Calculate the offset register value:
Mode = 0 (normal mode):
Offset value = Eppm / 2.17
Mode = 1 (course mode)
Offset value = Eppm / 4.34
013aaa684
Fig 20. Offset calibration calculation workflow
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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