'alarm' related articles 1

  1. 2007/03/24 DS1305 - Serial Alarm Real Time Clock (RTC)
FEATURES
* Real time clock counts seconds, minutes, hours, date of the month, month, day of the week and year with leap year compensation valid up to 2100
* 96-byte nonvolatile RAM for data storage
* Two time-of-day alarms programmable on combination of seconds, minutes, hours and day of the week
* Serial interface supports Motorola serial peripheral interface (SPI) serial data ports or standard 3-wire interface
* Burst mode for reading/writing successive addresses in clock/RAM
* Dual power supply pins for primary and backup power supplies
* Optional trickle charge output to backup supply
* 2.0 - 5.5V operation
* Optional industrial temperature range -40°C to +85°C
* Available in space-efficient, 20-pin TSSOP package
* Recognized by Underwriters Laboratory

PIN DESCRIPTION
VCC1 - Primary Power Supply
VCC2 - Backup Power Supply
VBAT - +3V Battery Input
VCCIF - Interface Logic Power Supply Input
GND - Ground
X1, X2 - 32.768 kHz Crystal Connection
INT0 - Interrupt 0 Output
INT1 - Interrupt 1 Output
SDI - Serial Data In
SDO - Serial Data Out
CE - Chip Enable
SCLK - Serial Clock
SERMODE - Serial Interface Mode
PF - Power Fail Output

DESCRIPTION
The DS1305 Serial Alarm Real Time Clock provides a full BCD clock calendar which is accessed via 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 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. In addition 96 bytes of nonvolatile RAM are provided for data storage.

An interface logic power supply input pin (VCCIF) allows the DS1305 to drive SDO and PF pins to a level that is compatible with the interface logic. This allows an easy interface to 3-volt logic in mixed supply systems.

The DS1305 offers dual power supplies as well as a battery input pin. The dual power supplies support a programmable trickle charge circuit which allows a rechargeable energy source (such as a super cap or rechargeable battery) to be used for a backup supply. The VBAT pin allows the device to be backed up by a non-rechargeable battery. The DS1305 is fully operational from 2.0 to 5.5 volts.

Two programmable time of day alarms are provided by the DS1305. 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. The time of day alarms can be programmed to assert two different interrupt outputs or to assert one common interrupt output. Both interrupt outputs operate when the device is powered by VCC1, VCC2, or VBAT.

The DS1305 supports a direct interface to Motorola SPI serial data ports or standard 3-wire interface. A straightforward address and data format is implemented in which data transfers can occur 1 byte at a time or in multiple-byte burst mode.

DS1305 DS1305N DS1305E DS1305EN

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