RV5C339A Datasheet, PDF (34/51 Pages) RICOH electronics devices division – 3-WIRE SERIAL INTERFACE REAL-TIME CLOCK ICs WITH VOLTAGE MONITORING FUNCTION

RV5C339A
2.4-2 When Oscillation Frequency is Equal to Target Frequency (There is Neither a Time Count Gain nor
a Time Count Loss)
Writing the oscillation adjustment value setting of “0”, “+1”, “–64”, or “–63” to the oscillation adjustment register
disables the oscillation adjustment circuit.
2.4-3 When Oscillation Frequency is Lower than Target Frequency (There is a Time Count Loss)
(Oscillation frequency – Target frequency)
Oscillation adjustment value*³ = _{Oscillation frequency × 3.051 × 10–6}
._{= (Oscillation frequency – Target frequency) × 10}
Oscillation adjustment value calculations are exemplified below.
(1) For an oscillation frequency of 32768.85Hz and a target frequency of 32768.05Hz:
Oscillation adjustment value = (32768.85 – 32768.05 + 0.1) / (32768.85 × 3.051 × 10^–6) ^.= (32768.85 – 32768.05) × 10 + 1
._{= 9.001 = 9}
In this instance, write the settings of “0, 0, 0, 1, 0, 0, 1” to the F6, F5, F4, F3, F2, F1, and F0 bits in the oscillation
adjustment register. Thus, an appropriate oscillation adjustment value in the presence of any time count gain
represents a distance from 01h.
(2) For an oscillation frequency of 32763.95Hz and a target frequency of 32768.05Hz:
Oscillation adjustment value = (32763.95 – 32768.05) / (32763.95 × 3.051 × 10^–6) ^.= (32763.95 – 32768.05) × 10
= –41.015 =^. –41
To represent an oscillation adjustment value of –41 in 7-bit coded decimal notation, subtract 41(29h) from
128(80h) to obtain 57h. In this instance, write the settings of “1, 0, 1, 0, 1, 1, 1” in the F6, F5, F4, F3, F2, F1, and F0
bits in the oscillation adjustment register. Thus, an appropriate oscillation adjustment value in the presence of
any time count loss represents a distance from 80h.
Oscillation adjustment involves an adjustment differential of approximately ±1.5ppm from the target frequency
at normal temperature.
Notes
1) Oscillation adjustment does not affect the frequency of 32.768-kHz clock pulses output from the 32KOUT
pin.
2) Oscillation adjustment value range: When the oscillation frequency is higher than the target frequency
(causing a time count gain), an appropriate time count gain ranges from –3.05ppm to –189.2ppm with the
settings of “0, 0, 0, 0, 0, 1, 0” to “0, 1, 1, 1, 1, 1, 1” written to the F6, F5, F4, F3, F2, F1, and F0 bits in the
oscillation adjustment register, thus allowing correction of a time count gain of up to +189.2ppm.
Conversely, when the oscillation frequency is lower than the target frequency (causing a time count loss),
an appropriate time count gain ranges from +3.05ppm to +189.2ppm with the settings of “1, 1, 1, 1, 1, 1, 1”
to “1, 0, 0, 0, 0, 1, 0” written to the F6, F5, F4, F3, F2, F1, and F0 bits in the oscillation adjustment register,
thus allowing correction of a time count loss of up to –189.2ppm.
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