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RV5C387A Datasheet(PDF) 7 Page - RICOH electronics devices division |
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RV5C387A Datasheet(HTML) 7 Page - RICOH electronics devices division |
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7 / 49 page  7 RV5C387A GENERAL DESCRIPTION 1. Interface with CPU The RV5C387A 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 output of 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 ≥2.5V) of SCL enables data transfer in I2C bus fast mode. 2. Clock and Calendar Function The RV5C387A 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. Also available is the 1900/2000 identification bit for Year 2000 compliance. 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. 3. Alarm Function The RV5C387A incorporates an alarm circuit configured to generate interrupt signals to the CPU for output from the INTRB or INTRC pin at preset times. The alarm 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 signal outputs from INTRB pin, and the Alarm_D signal outputs from INTRC pin. The current INTRB or INTRC pin conditions specified by these two registers can be checked from the CPU by using a polling function. 4. High-precision Oscillation Adjustment Function The RV5C387A has built-in oscillation stabilization capacitors (CG and CD), which can be connected to an external crystal oscillator to configure an oscillation circuit. To correct deviations in the oscillation frequency of the crystal oscillator, the oscillation adjustment circuit is configured to allow correction of a time count gain or loss (up to ±1.5ppm at 25˚C) from the CPU within a maximum range of approximately ±189ppm in increments of approximately 3ppm. Such oscillation frequency adjustment in each system has the following advantages: · Allows timekeeping with much higher precision than conventional real-time clocks while using a crysta l oscillator with a wide range of precision variations. · Corrects seasonal frequency deviations through seasonal oscillation adjustment. · Allows timekeeping with higher precision particularly in systems with a temperature sensing function through oscillation adjustment in tune with temperature fluctuations. |
Similar Part No. - RV5C387A_03 |
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Similar Description - RV5C387A_03 |
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