Datasheet

Product data sheet Rev. 7 — 19 December 2014 40 of 86

NXP Semiconductors

PCF2129

Accurate RTC with integrated quartz crystal for industrial applications

A most common application of the timestamp function is described in Ref. 3 “AN11186”.

See Section 8.12.5

for a description of interrupt generation from the timestamp function.

8.11.1 Timestamp flag

1. When the TS input pin is driven to an intermediate level between the power supply

and ground, either on the falling edge from V

or on the rising edge from ground,

then the following sequence occurs:

a. The actual date and time are stored in the timestamp registers.

b. The timestamp flag TSF1 (register Control_1) is set.

c. If the TSIE bit (register Control_2) is active, an interrupt on the INT

pin is

generated.

The TSF1 flag can be cleared by command. Clearing the flag clears the interrupt.

Once TSF1 is cleared, it will only be set again when a new negative or positive edge

on pin TS

is detected.

2. When the TS

input pin is driven to ground, the following sequence occurs:

a. The actual date and time are stored in the timestamp registers.

b. In addition to the TSF1 flag, the TSF2 flag (register Control_2) is set.

c. If the TSIE bit is active, an interrupt on the INT

pin is generated.

The TSF1 and TSF2 flags can be cleared by command; clearing both flags clears the

interrupt. Once TSF2 is cleared, it will only be set again when TS

pin is driven to

ground once again.

8.11.2 Timestamp mode

The timestamp function has two different modes selected by the control bit TSM

(timestamp mode) in register Timestp_ctl:

• If TSM is logic 0 (default): in subsequent trigger events without clearing the timestamp

flags, the last timestamp event is stored

• If TSM is logic 1: in subsequent trigger events without clearing the timestamp flags,

the first timestamp event is stored

The timestamp function also depends on the control bit BTSE in register Control_3, see

Section 8.11.4