PCF2127AT/1 NXP [NXP Semiconductors], PCF2127AT/1 Datasheet - Page 5

• Manufacturer Part Number: PCF2127AT/1
• Description: Integrated RTC, TCXO and quartz crystal
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
8. Functional description
PCF2127A_2
Product data sheet
The PCF2127A is a Real Time Clock (RTC) and calendar with an on-chip Temperature
Compensated Crystal (Xtal) Oscillator (TCXO) and a 32.768 kHz quartz crystal integrated
into the same package.
Address and data are transferred by a selectable 400 kHz Fast-mode I
SPI-bus with separate data input and output (see
SPI-bus is 6.5 Mbit/s.
The PCF2127A contains 30 8-bit registers that are used for many different functions, such
as clock, alarm, watchdog, timer, timestamp etc. (see
The PCF2127A has an output reset pin: the output reset is activated on Power-On Reset
(POR), and whenever the oscillator is stopped (see
The PCF2127A features 512 bytes of general purpose static RAM, which is battery
backed and can be used independently of the RTC functionality (see
The PCF2127A has a backup battery input pin and backup battery switch-over circuit
which monitors the main power supply and automatically switches to the backup battery
when a power failure condition is detected (see
maintained even when the main power supply is interrupted.
A battery low detection circuit monitors the status of the battery (see
the battery voltage goes below a certain threshold value, a flag is set to indicate that the
battery must be replaced. This can be used to ensure the integrity of the data during
periods of battery backup. A power failure detection circuit monitors the voltage of the
power fail input pin PFI. When the voltage on the power fail input pin PFI goes below an
internal reference (1.25 V), the power fail output pin PFO is activated (see
All information provided in this document is subject to legal disclaimers.
Rev. 02 — 7 May 2010
Integrated RTC, TCXO and quartz crystal
Section
Section
Section
Section
8.6.1). Accurate timekeeping is
9). The maximum speed of the
8.8).
8.1).
PCF2127A
Section
Section
2
© NXP B.V. 2010. All rights reserved.
C-bus or a 3 line
Section
8.6.3). When
8.5).
8.6.4).
5 of 80