R2023K/T
GENERAL DESCRIPTION
•
Interface with CPU
The R2023K/T 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 I
2
C bus fast mode.
•
Clock and Calendar Function
The R2023K/T 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 R2023K/T 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 R2023K/T 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.
•
Power-on Reset, Oscillation Halt Sensing Function and Supply Voltage Monitoring Function
The R2023K/T incorporates an oscillation halt sensing circuit equipped with internal registers configured to record
any past oscillation halt.
Power on reset function reset the control resisters when the system is powered on from 0V. At the same time, the
fact is memorized to the resister as a flag, thereby identifying whether they are powered on from 0V or battery
backed-up.
The R2023K/T also incorporates a supply voltage monitoring circuit equipped with internal registers configured to
record any drop in supply voltage below a certain threshold value. Supply voltage monitoring threshold settings can
be selected between 1.6V and 1.3V through internal register settings. The sampling rate is normally 1s.
The oscillation halt sensing circuit and the power-on reset flag are configured to confirm the established
invalidation of time data in contrast to the supply voltage monitoring circuit intended to confirm the potential
invalidation of time data. Further, the supply voltage monitoring circuit can be applied to battery supply voltage
monitoring.
9
RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
