pca2125 NXP Semiconductors, pca2125 Datasheet - Page 23

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

NXP Semiconductors
PCA2125_00
Preliminary data sheet
6.8 Clock output
A programmable square wave is available at pin CLKOUT. Operation is controlled by the
COF control bits in the control register. Frequencies of 32.768 kHz (default) down to 1Hz
can be generated for use as a system clock, micro-controller clock, input to a charge
pump, or for calibration of the oscillator.
CLKOUT is an open drain output and enabled at power-on. When disabled the output is
high impedance (Hi-Z).
The duty cycle of the selected clock is not controlled however, due to the nature of the
clock generation, all but the 32.768kHz frequencies will be 50:50.
The ‘stop’ function can also affect the CLKOUT signal, depending on the selected
frequency. When ‘stop’ is active, the CLKOUT pin will generate a continuous 0 for those
frequencies that can be stopped. For more details see
Table 37:
COF[2:0]
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
CLKOUT frequency selection
CLKOUT FREQUENCY, Hz
32768
16384
8192
4096
2048
1024
1
CLKOUT = 0
Rev. 00.11 — 30 January 2007
Typical duty cycle
High% : Low%
60:40 to 40:60
50:50
50:50
50:50
50:50
50:50
50:50
Section
SPI Real time clock / calendar
6.10.
Effect of ‘stop’
No effect
No effect
No effect
CLKOUT = 0
CLKOUT = 0
CLKOUT = 0
CLKOUT = 0
PCA2125
© NXP B.V. 2007. All rights reserved.
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