pca2125 NXP Semiconductors, pca2125 Datasheet - Page 25

• Manufacturer Part Number: pca2125
• Description: Spi Real Time Clock / Calendar Semiconductors
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA2125_00
Preliminary data sheet
6.10 ’stop’ bit function
The function of the stop bit is to allow for accurate starting of the time circuits. The stop
function will cause the upper part of the pre-scaler, F2 to F14, to be held in reset and thus
no 1Hz ticks will be generated. The time circuits can then be set and will not increment
until the stop is released. (see
Stop will not affect the output of 32768 Hz, 16384 Hz or 8192 Hz (see
The lower two stages of the pre-scaler, F
interface is asynchronous to the crystal oscillator, the accuracy of re-starting the time
circuits will be between 0 and one 8192Hz cycle (see
The first increment of the time circuits is between 0.499888 s and 0.500000 s after stop is
released. The uncertainty is caused by the pre-scaler bits F
Table
Table 38.
Stop
Clock is running normally.
0
Stop is activated by user. F
1
Fig 16. stop bit
Fig 17. stop bit release timing
38).
OSC
Pre-scaler
F
01-0000111010100
xx-0000000000000
0
F
First increment of time circuits after stop release
1
stop released
, F
2
8192 Hz
to F
14
Rev. 00.11 — 30 January 2007
[1]
0
F
F
0
1Hz tick Time
1
are not reset and values can not be predicted externally.
Figure
F
1
16).
HH:MM:SS
12:45:12
DETECTOR
OSC STOP
0
and F
RES
0-122 µs
F
2
1
, are not reset and because the SPI
16384 Hz
Comment
Pre-scaler counting normally
Pre-scaler is reset. Time circuits are
frozen.
8192 Hz
reset
512 Hz
Figure
SPI Real time clock / calendar
0
RES
17).
and F
F
13
CLKOUT source
1
not being reset (see
RES
PCA2125
Section
F
001aaf912
© NXP B.V. 2007. All rights reserved.
14
001aaf911
1 Hz tick
stop
6.8).
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