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 7 of 86
NXP Semiconductors
PCF2129
Accurate RTC with integrated quartz crystal for industrial applications
32.768 kHz (default) down to 1 Hz for use as system clock, microcontroller clock, and
so on, can be chosen (see Table 15
).
• The registers at addresses 10h and 11h are used for the watchdog timer functions.
The watchdog timer has four selectable source clocks allowing for timer periods from
less than 1 ms to greater than 4 hours (see Table 52
). An interrupt is generated when
the watchdog times out.
• The registers at addresses 12h to 18h are used for the timestamp function. When the
trigger event happens, the actual time is saved in the timestamp registers (see
Section 8.11
).
• The register at address 19h is used for the correction of the crystal aging effect (see
Section 8.4.1
).
• The registers at addresses 1Ah and 1Bh are for internal use only.
• The registers Seconds, Minutes, Hours, Days, Months, and Years are all coded in
Binary Coded Decimal (BCD) format to simplify application use. Other registers are
either bit-wise or standard binary.
When one of the RTC registers is written or read, the content of all counters is temporarily
frozen. This prevents a faulty writing or reading of the clock and calendar during a carry
condition (see Section 8.8.8
).