BLUENRG-LP datasheet(19/72 Pages) STMICROELECTRONICS

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1.18

Real-time clock (RTC)

The RTC is an independent BCD timer/counter. The RTC provides a time of day/clock/calendar with

programmable alarm interrupt. RTC includes also a periodic programmable wake-up flag with interrupt capability.

The RTC provides an automatic wake-up to manage all low power modes.

Two 32-bit registers contain seconds, minutes, hours (12- or 24-hour format), day (day of week), date (day of

month), month, and year, expressed in binary coded decimal format (BCD). The sub-second value is also

available in binary format. Compensations for 28-, 29- (leap year), 30-, and 31-day months are performed

automatically. Daylight saving time compensation can also be performed. Additional 32-bit registers contain the

programmable alarm sub seconds, seconds, minutes, hours, day, and date.

A digital calibration circuit with 0.95 ppm resolution is available to compensate for quartz crystal inaccuracy. After

power-on reset, all RTC registers are protected against possible parasitic write accesses. As long as the supply

voltage remains in the operating range, the RTC never stops, regardless of the device status (RUN mode, low

power mode or under system reset). The RTC counter does not freeze when CPU is halted by a debugger.

1.19

Inter-integrated circuit interface (I2C)

The BlueNRG-LP embeds two I2Cs. The I2C bus interface handles communications between the microcontroller

and the serial I2C bus. It controls all I2C bus-specific sequencing, protocol, arbitration and timing.

The I2C peripheral supports:

•

I2C bus specification and user manual rev. 5 compatibilities:

–

Slave and master modes

–

Multimaster capability

–

Standard-mode (Sm), with a bitrate up to 100 kbit/s

–

Fast-mode (Fm), with a bitrate up to 400 kbit/s

–

Fast-mode Plus (fm+), with a bitrate up to 1 Mbit/s and 20 mA output driver I/Os

–

7-bit and 10-bit addressing mode

–

Multiple 7-bit slave addresses (2 addresses, 1 with configurable mask)

–

All 7-bit address acknowledge mode

–

General call

–

Programmable setup and hold times

–

Easy to use event management

–

Optional clock stretching

–

Software reset

•

System management Bus (SMBus) specification rev 2.0 compatibility:

–

Hardware PEC (Packet Error Checking) generation and verification with ACK control

–

Address resolution protocol (ARP) support

–

Host and device support

–

SMBus alert

–

Timeouts and idle condition detection

•

Power system management protocol (PMBusTM) specification rev 1.1 compatibility

•

Independent clock: a choice of independent clock sources allowing the I2C communication speed to be

independent from the PCLK reprogramming

•

Programmable analog and digital noise filters

•

1-byte buffer with DMA capability

1.20

Universal synchronous/asynchronous receiver transmitter (USART)

USART offers flexible full-duplex data exchange with external equipment requiring an industry standard NRZ

asynchronous serial data format. USART is able to communicate with a speed up to 2 Mbit/s. Furthermore,

USART is able to detect and automatically set its own baud rate, based on the reception of a single character.

The USART peripheral supports:

•

Synchronous one-way communication

BlueNRG-LP

Real-time clock (RTC)

DS13282 - Rev 2

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