oscillation adjustment circuit can be disabled by writing the settings of 鈥?/div>
鈥?(鈥?/div>
*
鈥?representing 鈥?鈥?or
鈥?鈥? to the F
6
, F
5
, F
4
, F
3
, F
2
, F
1
, and F
0
bits in the oscillation adjustment circuit. Conversely, when such oscillation
adjustment is to be made, an appropriate oscillation adjustment value can be calculated by the equation below for
writing to the oscillation adjustment circuit.
2.4-1 When Oscillation Frequency *
1
is Higher than Target Frequency *
2
(There is a Time Count Gain)
Oscillation adjustment value*
3
=
.
(Oscillation frequency 鈥?Target frequency + 0.1)
Oscillation frequency
脳
3.051
脳
10
鈥?
.
(Oscillation frequency 鈥?Target frequency)
脳
10 + 1
=
*
1)
*
2)
Oscillation frequency:
Target frequency:
Frequency of clock pulses output from the 32KOUT pin at normal temperature in the manner described in 鈥?.2
Measurement of Oscillation Frequency鈥?
Desired frequency to be set. Generally, a 32.768-kHz crystal oscillator has such temperature characteristics as to have
the highest oscillation frequency at normal temperature. Consequently, the crystal oscillator is recommended to have
target frequency settings on the order of 32.768 to 32.76810kHz (+3.05ppm relative to 32.768kHz). Note that the target
frequency differs depending on the environment or location where the equipment incorporating the real-time clocks is
expected to be operated.
*
3)
Oscillation adjustment value: Value that is to be finally written to the F
0
to F
6
bits in the oscillation adjustment register and is represented in 7-bit coded
decimal notation.
30