R2023T-E2-F Datasheet, PDF (10/56 Pages) RICOH electronics devices division – 2-wire Serial Interface Real Time Clock IC

R2023x
* R2023K (FFP12) is the discontinued product as of February, 2016.
GENERAL DESCRIPTION
• Interface with CPU
The R2023x is connected to the CPU by two signal lines, SCL and SDA, through which it reads and writes
data from and to the CPU. Since the I/O pin of SDA is open drain, data interfacing with a CPU different supply
voltage is possible by applying pull-up resistors on the circuit board. The maximum clock frequency of 400kHz
(at VDD≥1.7v) of SCL enables data transfer in I²C bus fast mode.
• Clock and Calendar Function
The R2023x reads and writes time data from and to the CPU in units ranging from seconds to the last two
digits of the calendar year. The calendar year will automatically be identified as a leap year when its last two
digits are a multiple of 4. Consequently, leap years up to the year 2099 can automatically be identified as such.
*) The year 2000 is a leap year while the year 2100 is not a leap year.
• Alarm Function
The R2023x incorporates the alarm interrupt circuit configured to generate interrupt signals to the CPU at
preset times. The alarm interrupt circuit allows two types of alarm settings specified by the Alarm_W registers
and the Alarm_D registers. The Alarm_W registers allow week, hour, and minute alarm settings including
combinations of multiple day-of-week settings such as "Monday, Wednesday, and Friday" and "Saturday and
Sunday". The Alarm_D registers allow hour and minute alarm settings. The Alarm_W outputs from INTRB pin,
and the Alarm_D outputs from INTRA pin. Each alarm function can be checked from the CPU by using a
polling function.
• High-precision Oscillation Adjustment Function
The R2023x has built-in oscillation stabilization capacitors (CG and CD), which can be connected to an external
crystal oscillator to configure an oscillation circuit. Two kinds of accuracy for this function are alternatives. To
correct deviations in the oscillator frequency of the crystal, the oscillation adjustment circuit is configured to
allow correction of a time count gain or loss (up to ±1.5ppm or ±0.5ppm at 25°C) from the CPU. The maximum
range is approximately ±189ppm (or ±63ppm) in increments of approximately 3ppm (or 1ppm). Such oscillation
frequency adjustment in each system has the following advantages:
* Allows timekeeping with much higher precision than conventional RTCs while using a crystal oscillator with
a wide range of precision variations.
* Corrects seasonal frequency deviations through seasonal oscillation adjustment.
* Allows timekeeping with higher precision particularly with a temperature sensing function out of RTC, through
oscillation adjustment in tune with temperature fluctuations.
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