DS1306
DESCRIPTION
The DS1306 serial alarm real-time clock (RTC) provides a full binary coded decimal (BCD) clock
calendar that is accessed by a simple serial interface. 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 fewer than 31 days, including corrections for leap year. The clock operates in either the 24-
hour or 12-hour format with AM/PM indicator. In addition, 96 bytes of NV RAM are provided for data
storage.
An interface logic power-supply input pin (V
CCIF
) allows the DS1306 to drive SDO and 32kHz pins to a
level that is compatible with the interface logic. This allows an easy interface to 3V logic in mixed supply
systems. The DS1306 offers dual-power supplies as well as a battery-input pin. The dual-power supplies
support a programmable trickle charge circuit that allows a rechargeable energy source (such as a super
cap or rechargeable battery) to be used for a backup supply. The V
BAT
pin allows the device to be backed
up by a non-rechargeable battery. The DS1306 is fully operational from 2.0V to 5.5V.
Two programmable time-of-day alarms are provided by the DS1306. Each alarm can generate an
interrupt on a programmable combination of seconds, minutes, hours, and day. “Don’t care” states can be
inserted into one or more fields if it is desired for them to be ignored for the alarm condition. A 1Hz and a
32kHz clock output are also available.
The DS1306 supports a direct interface to SPI serial data ports or standard 3-wire interface. An easy-to-
use address and data format is implemented in which data transfers can occur 1 byte at a time or in
multiple-byte burst mode.
OPERATION
The block diagram in Figure 1 shows the main elements of the serial alarm RTC. The following
paragraphs describe the function of each pin.
Figure 1. BLOCK DIAGRAM
1Hz
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MAXIM [ MAXIM INTEGRATED PRODUCTS ]
