The low-voltage serial-peripheral interface (SPI?)
DS1390/DS1391/DS1394 and the low-voltage 3-wire
DS1392/DS1393 real-time clocks (RTCs) are clocks/calendars
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 DS1390, a single open-drain
output provides a CPU interrupt or a square wave at
one of four selectable frequencies. The DS1391
replaces the SQW/INT pin with a RST output/
debounced input.
The DS1390, DS1391, and DS1394 are programmed
serially through an SPI-compatible, bidirectional bus.
The DS1392 and DS1393 communicate over a 3-wire
serial bus, and the extra pin is used for either a separate
interrupt pin or a RST output/debounced input.