Micro Crystal
Ultra Small Real-Time Clock Module with SPI-Bus Interface
RV-8063-C7
October 2018
36/58
Rev. 1.1
CLKOUT FREQUENCY SELECTION
4.11.
A programmable square wave is available at pin CLKOUT. Operation is controlled by the FD field in the register
Control2. Frequencies of 32.768 kHz (default) down to 1 Hz can be generated for use as a system clock,
microcontroller clock, input to a charge pump, or for calibration of the crystal oscillator.
Pin CLKOUT is a push-pull output and enabled at power-on. CLKOUT can be disabled by setting the FD field to
111 or by setting CLKOE LOW. When disabled, the CLKOUT is LOW.
The duty cycle of the selected clock is not controlled. However, due to the nature of the clock generation, all are 50
: 50 except the 32.768 kHz frequency.
The STOP bit function can also affect the CLKOUT signal, depending on the selected frequency. When the STOP
bit is set logic 1, the CLKOUT pin generates a continuous LOW for those frequencies that can be stopped (for more
details, see STOP BIT FUNCTION).
FD
CLKOUT Frequency
Typical duty cycle
Effect of STOP bit
000
32.768 kHz
– Default value
50 ±10 %
no effect
001
16.384 kHz
50 %
no effect
010
8.192 kHz
50 %
no effect
011
4.096 kHz
50 %
CLKOUT = LOW
100
2.048 kHz
50 %
CLKOUT = LOW
101
1.024 kHz
50 %
CLKOUT = LOW
110
1 Hz
(1)
50 %
CLKOUT = LOW
111
CLKOUT = LOW
-
-
(1)
1 Hz clock pulses are affected by compensation pulses (see FREQUENCY OFFSET COMPENSATION).
