PCF8564AUSLASH10ABSLASH1 datasheet(18/48 Pages) NXP

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PCF8564A

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Product data sheet

Rev. 3 — 26 August 2013

18 of 48

NXP Semiconductors

PCF8564A

Real time clock and calendar

6. Read time registers to see the first change.

7. Apply 64 clock pulses to CLKOUT.

8. Read time registers to see the second change.

Repeat 7 and 8 for additional increments.

8.10 STOP bit function

The function of the STOP bit is to allow for accurate starting of the time circuits. The STOP

bit function will cause the upper part of the prescaler (F2 to F14) to be held in reset and

thus no 1 Hz ticks will be generated (see Figure 8). The time circuits can then be set and

will not increment until the STOP bit is released (see Figure 9 and Table 27).

The STOP bit function will not affect the output of 32.768 kHz on CLKOUT, but will stop

the generation of 1.024 kHz, 32 Hz and 1 Hz.

The lower two stages of the prescaler (F0 and F1) are not reset and because the I2C-bus

is asynchronous to the crystal oscillator, the accuracy of re-starting the time circuits will be

between zero and one 8.192 kHz cycle (see Figure 9).

Fig 8.

STOP bit functional diagram

Fig 9.

STOP bit release timing

PCF8564AU/10AB/1 Datasheet(PDF) 18 Page - NXP Semiconductors