描述 Description

The low-voltage serial-peripheral interface (SPI?) AT1390/AT1391/AT1394 and the low-voltage 3-wire AT1392/AT1393 real-time clocks (RTCs) are clocks/cal- endars that provide hundredths of a second, seconds, minutes, hours, day, date, month, and year information. The date at the end of the month 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 an AM/PM indicator. One programmable time-of-day alarm is provided. A temperature-compensated voltage reference monitors the status of VCC and automatically disables the bus interface and switches to the backup supply if a power failure is detected. On the AT1390, a single open-drain output provides a CPU interrupt or a square wave at one of four selectable frequencies. TheAT1391replaces the SQW/INT pin with a RST output/debounced input.
The AT1390, AT1391, and AT1394 are programmed serially through an SPI-compatible, bidirectional bus. The AT1392 and AT1393 communicate over a 3-wire serial bus, and the extra pin is used for either a sepa- rate interrupt pin or a RST output/debounced input. All five devices are available in a 10-pin μSOP package, and are rated over the industrial temperature range.