pcf2123 NXP Semiconductors, pcf2123 Datasheet - Page 32

• Manufacturer Part Number: pcf2123
• Description: Spi Real Time Clock/calendar
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF2123_1
Product data sheet
9.13 STOP bit function
Operation example:
Repeat 7 and 8 for additional increments.
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 (F
thus no 1 Hz ticks will be generated. The time circuits can then be set and will not
increment until the STOP bit is released (see
The STOP bit function will not affect the output of 32.768 kHz, 16.384 kHz or 8.192 kHz
(see
The lower two stages of the prescaler (F
is asynchronous to the crystal oscillator, the accuracy of re-starting the time circuits will be
between 0 and one 8.192 kHz cycle (see
1. Set EXT_TEST test mode (register Control_1, bit EXT_TEST = 1).
2. Set STOP (Control_1, bit STOP = 1).
3. Clear STOP (Control_1, bit STOP = 0).
4. Set time registers to desired value.
5. Apply 32 clock pulses to pin CLKOUT.
6. Read time registers to see the first change.
7. Apply 64 clock pulses to pin CLKOUT.
8. Read time registers to see the second change.
Fig 20. STOP bit
Section
OSC
9.10).
Rev. 01 — 19 November 2008
F
0
F
1
DETECTOR
OSC STOP
0
Figure
and F
Figure 21
RES
F
1
2
21).
) are not reset and because the SPI-bus
16384 Hz
8192 Hz
oscillator stop flag
512 Hz
2
and
to F
SPI Real time clock/calendar
Table
14
RES
F
13
) to be held in reset and
40).
CLKOUT source
RES
F
PCF2123
© NXP B.V. 2008. All rights reserved.
14
001aai556
1 Hz tick
stop
32 of 54