What are Actual Time Clocks?

Serious time clocks (RTC), as the name recommends are clock modules. The DS1307 genuine time clock (RTC) IC is undoubtedly an 8 pin unit applying an I2C interface. The DS1307 is actually a low-power clock/calendar with 56 bytes of battery backup SRAM. The clock/calendar provides seconds, minutes, several hours, day, day, thirty day period and year qualified facts. The end day of every thirty day period is quickly adjusted, especially for months with a lot less than 31 days.

They are offered as built-in circuits (ICs) and supervise timing similar to a clock and also operate day like a calendar. The most crucial advantage of RTC is always that they have an arrangement of battery backup which retains the clock/calendar operating regardless of whether there may be power failure. An exceptionally minor latest is required for trying to keep the RTC animated. We could come across these RTCs in several apps like embedded devices and personal computer mother boards, etc. On this posting we are going to see about 1 with the serious time clock (RTC), i.e. DS1307.

Pin Description of DS1307:

Pin one, two: Connections for typical 32.768 kHz quartz crystal. The interior oscillator circuitry is intended for operation using a crystal acquiring a specified load capacitance of 12.5pF. X1 may be the input for the oscillator and can alternatively be related to an external 32.768 kHz oscillator. The output from the interior oscillator, X2 is drifted if an exterior oscillator is related to X1.

Pin three: Battery input for any typical 3V lithium cell or other energy resource. Battery voltage need to be in between 2V and 3.5V for ideal operation. The nominal create protect trip issue voltage at which accessibility for the RTC and user RAM is denied is set via the internal circuitry as 1.25 x VBAT nominal. A lithium battery with 48mAhr or greater will backup the DS1307 for in excess of 10 yrs within the absence of energy at 25oC. UL recognized to ensure in opposition to reverse charging present when utilized as a portion of conjunction having a lithium battery.

Pin 4: Floor.

Pin 5: Serial data input/output. The input/output to the I2C serial interface may be the SDA, which can be open up drain and involves a pull up resistor, allowing a pull up voltage upto 5.5V. In spite of the voltage on VCC.

Pin six: Serial clock enter. It truly is the I2C interface clock enter and is utilized in data synchronization.

Pin 7: Sq. wave/output driver. When enabled, the SQWE bit established to 1, the SQW/OUT pin outputs one of 4 square-wave frequencies (1Hz, four kHz, 8 kHz, and 32 kHz). This really is also open up drain and demands an external pull-up resistor. It demands application of both Vcc or Vb at to function SQW/OUT, having an allowable pull up voltage of five.5V and may be left floating, if not employed.

Pin 8: Key electric power source. When voltage is used within normal limits, the device is entirely available and data could be published and study. When a backup provide is linked to your unit and VCC is down below VTP, read through and writes are inhibited. Nevertheless at lower voltages, the timekeeping function still capabilities.

Characteristics:

Programmable sq. wave output sign

Automatic power-fail detect and change circuitry

Consumes much less than 500nA in battery backup mode with oscillator running

Readily available in 8-pin DIP or SOIC

Underwriters Laboratory (UL) recognized

Real-time clock (RTC) counts seconds, minutes, several hours, date on the thirty day period, month, day in the week, and 12 months with leap-year payment valid nearly 2100

56-byte non-volatile RAM for facts storage

Two-wire interface (I2C)

Utilizing the DS1307 is primarily published to and read the registers of this chip. The memory contains all 64 DS1307 8-bit registers are addressed from 0 to 63 (from 00H to 3FH the hexadecimal process). The initial eight registers are employed for the clock register the remaining 56 vacant may be used as RAM contains temporary variable if desired. The very first seven registers incorporate data in regards to the time of the clock which includes: seconds, minutes, hrs, secondary, day, thirty day period and calendar year. The DS1307 contain numerous factors these types of as electric power circuits, oscillator circuits, logic controller and I2C interface circuit along with the address pointer register (or RAM). Let?¡¥s see the functioning of DS1307.

Related links：

Authentic Time Clocks (RTCs) in Microcontroller Timers

Protection in RTCs

Actual Time Clock (RTC)

Develop a Real time Clock

Actual Time Clock (RTC) Vs. Clock: What On Earth Is The Primary Difference?