Overview
Real
Time Clock based on most popular RTC IC DS1307 which can maintain clock &
calendar information. Life of 3V battery is 10 years which maintains accurate
clock even without any external power. The clock/calendar provides seconds,
minutes, hours, day, date, month, and year information. The Interface to board
is simple I2C with SCK and SDA pins which can be interfaced with any
microcontroller easily.
Real Time Clock
Features:
- Real-Time Clock (RTC) Counts Seconds, Minutes, Hours,
Date of the Month, Month, Day of the week, and Year with Leap-Year
Compensation Valid Up to 2100.
- 56-Byte, Battery-Backed, Nonvolatile (NV) RAM for Data
Storage.
- I2C Serial Interface
- Automatic Power-Fail Detect and Switch Circuitry.
- Consumes Less than 500nA in Battery Backup Mode with
Oscillator Running.
PIN Out Details
Working
The DS1307 Serial
Real Time Clock is a low power, full BCD clock/calendar plus 56 bytes of
nonvolatile SRAM. Address and data are
transferred serially via a 2-wire bi-directional bus. The clock/calendar provides seconds, minutes,
hours, day, date, month, and year information.
The end of the month date is automatically adjusted for months with less
than 31 days, including corrections for leap year. The clock operates in either the 24-hour or
12-hour format with AM/PM indicator. The
DS1307 has a built-in power sense circuit which detects power failures and
automatically switches to the battery supply
OPERATION
The DS1307 operates as a slave device on the serial bus. Access is obtained by implementing a START
condition and providing a device identification code followed by a register
address. Subsequent registers can be
accessed sequentially until a STOP condition is executed. When VCC
falls below 1.25 x VBAT the
device terminates an access in progress and resets the device address counter. Inputs to the device will not be recognized at
this time to prevent erroneous data from being written to the device from an
out of tolerance system. When VCC falls below VBAT the device switches into a low current
battery backup mode. Upon power up, the
device switches from battery to VCC when VCC is greater than VBAT +0.2V and
recognizes inputs when VCC is greater than 1.25 x VBAT. The block diagram in Figure 1 shows the main
elements of the Serial Real Time Clock.
Block Diagram:
ATMEL Schematic
ATMEL CODE:
PIC Schematic:
PIC CODE:
