R2025S/D
Value that is to be finally written to the F0 to F6 bits in the Oscillation Adjustment Register and is represented
in 7-bit coded decimal notation.
(2) When Oscillation Frequency Is Equal To Target Frequency (Causing Time Count neither Gain nor Loss)
Oscillation adjustment value = 0, +1, -64, or –63
(3) When Oscillation Frequency Is Lower Than Target Frequency (Causing Time Count Loss)
Oscillation adjustment value = (Oscillation frequency - Target Frequency)
Oscillation frequency × 3.051 × 10-6
≈ (Oscillation Frequency – Target Frequency) × 10
Oscillation adjustment value calculations are exemplified below
(A) For an oscillation frequency = 32768.85Hz and a target frequency = 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 ((0),F6,F5,F4,F3,F2,F1,F0)=(0,0,0,0,1,0,0,1) in the oscillation adjustment
register. Thus, an appropriate oscillation adjustment value in the presence of any time count gain represents a
distance from 01h.
(B) For an oscillation frequency = 32762.22Hz and a target frequency = 32768.05Hz
Oscillation adjustment value = (32762.22 - 32768.05) / (32762.22 × 3.051 × 10-6)
≈ (32762.22 - 32768.05) × 10
= -58.325 ≈ -58
To represent an oscillation adjustment value of - 58 in 7-bit coded decimal notation, subtract 58 (3Ah) from 128
(80h) to obtain 46h. In this instance, write the settings of ((0),F6,F5,F4,F3,F2,F1,F0) = (0,1,0,0,0,1,1,0) in the
oscillation adjustment register. Thus, an appropriate oscillation adjustment value in the presence of any time
count loss represents a distance from 80h.
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.
If following 3 conditions are completed, actual clock adjustment value could be different from target
adjustment value that set by oscillator adjustment function.
3)
1. Using oscillator adjustment function
2. Access to R2025S/D at random, or synchronized with external clock that has no relation to R2025S/D, or
synchronized with periodic interrupt in pulse mode.
3. Access to R2025S/D more than 2 times per each second on average.
For more details, please contact to Ricoh.
• How to evaluate the clock gain or loss
The oscillator adjustment circuit is configured to change time counts of 1 second on the basis of the settings of
the oscillation adjustment register once in 20 seconds. The oscillation adjustment circuit does not effect the
frequency of 32768Hz-clock pulse output from the 32OUT pin. Therefore, after writing the oscillation adjustment
register, we cannot measure the clock error with probing 32KOUT clock pulses. The way to measure the clock
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RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
