Datasheet

PCF2129 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 7 — 19 December 2014 39 of 86
NXP Semiconductors
PCF2129
Accurate RTC with integrated quartz crystal for industrial applications
The following tables show what instruction must be sent to clear the appropriate flag.
[1] The bits labeled as - have to be rewritten with the previous values.
[1] The bits labeled as - have to be rewritten with the previous values.
8.11 Timestamp function
The PCF2129 has an active LOW timestamp input pin TS, internally pulled with an
on-chip pull-up resistor to V
oper(int)
. It also has a timestamp detection circuit which can
detect two different events:
1. Input on pin TS
is driven to an intermediate level between power supply and ground.
2. Input on pin TS
is driven to ground.
The timestamp function is enabled by default after power-on and it can be switched off by
setting the control bit TSOFF (register Timestp_ctl).
Table 54. Example values in register Control_2
Register Bit
7 6 5 4 3 2 1 0
Control_2 10110000
Table 55. Example to clear only AF (bit 4)
Register Bit
7 6 5 4 3 2 1 0
Control_2 1 0 1 0 0 0
[1]
0
[1]
0
Table 56. Example to clear only MSF (bit 7)
Register Bit
7 6 5 4 3 2 1 0
Control_2 0 0 1 1 0 0
[1]
0
[1]
0
(1) When using switches or push-buttons, it is recommended to connect a 1 nF capacitance to the TS
pin to ensure proper switching.
Fig 20. Timestamp detection with two push-buttons on the TS pin (for example, for
tamper detection)
3&[
76
SXVKEXWWRQ
FRQQHFWHGWR
FRYHU
SXVKEXWWRQ
FRQQHFWHGWR
FRYHU
9
RSHULQW
9
66
DDD
5
N

5
N

Q)
