PCA2129 datasheet(39/84 Pages) NXP

39 / 84 page

PCA2129

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Product data sheet

Rev. 5 — 19 December 2014

39 of 84

NXP Semiconductors

PCA2129

Automotive accurate RTC with integrated quartz crystal

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 PCA2129 has an active LOW timestamp input pin TS, internally pulled with an

on-chip pull-up resistor to Voper(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

Bit

Control_2

101

10000

Table 55.

Example to clear only AF (bit 4)

Bit

Control_2

0[1]

Table 56.

Example to clear only MSF (bit 7)

Bit

Control_2

0[1]

(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 19. Timestamp detection with two push-buttons on the TS pin (for example, for

tamper detection)

PCA2129 Datasheet(PDF) 39 Page - NXP Semiconductors