PCF8563 datasheet(18/45 Pages) NXP

18 / 45 page

PCF8563

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Product data sheet

Rev. 9 — 16 June 2011

18 of 45

NXP Semiconductors

PCF8563

Real-time clock/calendar

5. Apply 32 clock pulses to CLKOUT.

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 steps 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 11). The time circuits can then be set and

will not increment until the STOP bit is released (see Figure 12 and Table 26).

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 12).

Fig 11. STOP bit functional diagram

013aaa089

OSCILLATOR

OSCILLATOR STOP

DETECTOR

F13

RESET

F14

RESET

1024 Hz

32 Hz

1 Hz tick

STOP

CLKOUT source

reset

32768 Hz

1 Hz

Fig 12. STOP bit release timing

001aaf912

8192 Hz

stop released

μs to 122 μs

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