RV-8523 Datasheet, PDF (34/57 Pages) MICORO CRYSTAL SWITZERLAND – Real Time Clock

Micro Crystal
Real Time Clock / Calendar Module
RV-8523
9.8. CLKOUT FREQUENCY SELECTION
Clock output operation is controlled by the COF[2:0] in the Timer & CLKOUT register. Frequencies of 32.768 kHz
(default) down to 1 Hz can be generated (see table below) for use as a system clock, microcontroller clock, input to
a charge pump, or for calibration of the oscillator.
A programmable square wave is available at pin INT_1 and pin CLKOUT, which are both open-drain outputs. Pin
INT_1 has both functions of INT_1 and CLKOUT combined.
The duty cycle of the selected clock is not controlled but due to the nature of the clock generation, all clock
frequencies except 32.768 kHz have a duty cycle of 50 : 50.
The STOP bit function can also affect the CLKOUT signal, depending on the selected frequency. When STOP is
active, the INT_1 and CLKOUT pins will be high-impedance for all frequencies except of 32.768 kHz, 16.384 kHz
and 8.192 kHz. For more details, see section 9.10.
COF[2:0]
000²⁾
001
010
011
100
101
110
111
CLKOUT frequency (Hz)
32’768
16’384
8’192
4’096
1’024
32
1
CLKOUT disabled (high-Z)
Typical duty cycle¹⁾
60 : 40 to 40 : 60
50 : 50
50 : 50
50 : 50
50 : 50
50 : 50³⁾
50 : 50³⁾
1) _{Duty cycle definition: % HIGH-level time : % LOW-level time.}
2) _{Default value.}
3) _{Clock frequencies may be affected by offset correction.}
9.9. TIMER
Programmable timer characteristics:
TAQ[2:0]
TBQ[2:0]
Timer source
clock frequency
000
4.096
001
64
010
1
011
1_/60
111
110
1_/3600
100
Units
kHz
Hz
Hz
Hz
Hz
Minimum timer-period
(n = 1)
244
15.625
1
1
Units
µs
ms
s
min
1
hour
Effect of STOP bit
No effect
No effect
No effect
CLKOUT = high-Z
CLKOUT = high-Z
CLKOUT = high-Z
CLKOUT = high-Z
Maximum timer-period
(n = 255)
62.256
3.984
255
255
Units
ms
s
s
min
255
hour
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