Datasheet

Product data sheet Rev. 3 — 11 July 2013 11 of 47

NXP Semiconductors

PCF85063TP

Tiny Real-Time Clock/calendar

The duration of the timer is affected by the register Offset (see Section 8.2.3). Only when

OFFSET[6:0] has the value 00h the periods are consistent.

8.2.2.2 TF: timer flag

The timer flag (bit TF) is set logic 1 on the first trigger of MI or HMI and remains set until it

is cleared by command.

8.2.2.3 COF[2:0]: Clock output frequency

A programmable square wave is available at pin CLKOUT. Operation is controlled by the

COF[2:0] bits in the register Control_2. Frequencies of 32.768 kHz (default) down to 1 Hz

can be generated for use as a system clock, microcontroller clock, input to a charge

pump, or for calibration of the oscillator.

Pin CLKOUT is a push-pull output and enabled at power-on. CLKOUT can be disabled by

setting COF[2:0] to 111. When disabled, the CLKOUT is LOW.

The duty cycle of the selected clock is not controlled but due to the nature of the clock

generation, all clock frequencies except 32.768 kHz have a duty cycle of 50 : 50.

The STOP bit function can also affect the CLKOUT signal, depending on the selected

frequency. When the STOP bit is set logic 1, the CLKOUT pin generates a continuous

LOW for those frequencies that can be stopped. For more details of the STOP bit function,

see Section 8.2.1.2

[1] Duty cycle definition: % HIGH-level time : % LOW-level time.

[2] Default value.

[3] 1 Hz clock pulses are affected by offset correction pulses.

8.2.3 Register Offset

The PCF85063TP incorporates an offset register (address 02h) which can be used to

implement several functions, such as:

• Accuracy tuning

• Aging adjustment

• Temperature compensation

Table 11. CLKOUT frequency selection

COF[2:0] CLKOUT frequency (Hz) Typical duty cycle

[1]

Effect of STOP bit

000

[2]

32768 60 : 40 to 40 : 60 no effect

001 16384 50 : 50 no effect

010 8192 50 : 50 no effect

011 4096 50 : 50 CLKOUT = LOW

100 2048 50 : 50 CLKOUT = LOW

101 1024 50 : 50 CLKOUT = LOW

110 1

[3]

50 : 50 CLKOUT = LOW

111 CLKOUT = LOW - -