HOW DOES IT WORK?

RTC 14 Click as its foundation uses the ISL1221, a small micropower real-time clock that provides increased security features and tamper detection from Renesas. This device comes with time-stamp features in normal and battery modes, timing and crystal compensation, clock/calendar, power fail indicator, periodic or polled alarm, intelligent battery backup switching, and battery-backed user SRAM. With their enhanced security functionality, this RTC is ideally suited for various applications ranging from security, warranty monitoring, data collection, recording, and time-stamping single events, for example, recurring events such as the opening and closing a security door.

As mentioned before, the ISL1221 can time-stamp an external event by either issuing an output signal, containing the second, minute, hour, date, month, and year that the triggering event occurred, or by stopping the RTC registers from advancing at the moment the event occurs. The device also has calendar registers for a date, month, year, and day of the week, which is exceptionally accurate through 2099, with automatic leap year correction.

The alarm can be set to any clock/calendar value (for example, every minute, every Friday, or at 9:41 AM on September 10). The alarm status is available by checking the Status Register or available at the hardware interrupt pin routed to the INT pin of the mikroBUS™ socket. The alarm also contains a repeat mode allowing a periodic interrupt every minute, every hour, every day.

RTC 14 Click communicates with MCU using the standard I2C 2-Wire interface to read data and configure settings, supporting a Fast Mode operation up to 400kHz. Also, it has the frequency output programmable from 32.768kHz to 1/32Hz, available at the PWM pin of the mikroBUS™ socket and onboard header pin labeled as FO. This feature is used for various timing applications, including clocking the MCU in sleep mode, eliminating external crystal, and further reducing the BOM. To use features such as external event input or frequency output available on onboard headers, it is necessary to populate the resistors R8 and R9 and thus activate these functions on the headers.

The most common RTC configuration, like this one, is a battery-backed up, which maintains time and may hold data in 2 bytes of battery-backed SRAM provided for data storage. That's why, in addition to the ISL1221, the RTC 14 Click is equipped with a button cell battery holder compatible with the 3000TR battery holder, suitable for 12mm Coin Cell batteries.

This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the VCC SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to use the I2C communication lines properly. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.