PCF8523 Datasheet, PDF (27/66 Pages) NXP Semiconductors – Real-Time Clock (RTC) and calendar

NXP Semiconductors
PCF8523
Real-Time Clock (RTC) and calendar
8.8 Register Offset
The PCF8523 incorporates an offset register (address 0Eh), which can be used to
implement several functions, like:
• Aging adjustment,
• Temperature compensation,
• Accuracy tuning.
Table 26. Offset - offset register (address 0Eh) bit description
Bit
Symbol
Value
Description
7
MODE
0^[1]
offset is made once every two hours
1
offset is made once every minute
6 to 0 OFFSET[6:0]
see Table 27 offset value
[1] Default value.
Each LSB will introduce an offset of 4.34 ppm for MODE = 0 and 4.069 ppm for
MODE = 1. The values of 4.34 ppm and 4.069 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 27. Offset values
OFFSET[6:0]
Offset value in
decimal
0111111
+63
0111110
+62
:
:
000 0010
+2
000 0001
+1
000 0000
0^[1]
1111111
1
1111110
2
:
:
100 0001
63
100 0000
64
[1] Default mode.
Offset value in ppm
Every two hours
(MODE = 0)
+273.420
+269.080
:
+8.680
+4.340
0^[1]
4.340
8.680
:
273.420
277.760
Every minute
(MODE = 1)
+256.347
+252.278
:
+8.138
+4.069
0^[1]
4.069
8.138
:
256.347
260.416
The correction is made by adding or subtracting clock correction pulses, thereby changing
the period of a single second.
It is possible to monitor when correction pulses are applied. To enable correction interrupt
generation, bit CIE (register Control_1) has to be set logic 1. At every correction cycle a
1_{4096 s pulse will be generated on pin INT1. In the case that multiple correction pulses are}
applied, a ¹ï‚¤₄₀₉₆ s interrupt pulse will be generated for each correction pulse applied.
PCF8523
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 30 March 2011
© NXP B.V. 2011. All rights reserved.
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