DS1384

· Keeps track of hundredths of seconds, seconds, minutes, hours, days, date of the month, months, and years with leap year compensation valid up to 2100
· Watchdog timer restarts an out-of-control processor
· Alarm function schedules real-time related activities
· Programmable interrupts and square wave outputs
· Bytewide RAM-like access
· 50 bytes of on board user RAM
· Greater than 10 years timekeeping and data retention in the absence of power with small lithium coin cells
· Supports up to 128k x 8 of external static RAM
· All timekeeping registers and on board RAM are individually addressable via the address and data bus

Voltage on Any Pin Relative to Ground ...............-0.3V to +7.0V
Operating Temperature .........................................0°C to 70°C
Storage Temperature .......................................-20°C to +70°C
Soldering Temperature ................See J-STD-020A Specification

✻This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.

The DS1384 Watchdog Timekeeping Controller is a self-contained real time clock, alarm, watchdog timer, and interval timer which provides control of up to 128k x 8 of external low power CMOS static RAM in a 44-pin quad flat pack package. An external crystal and battery are the only components required to maintain time of day and RAM memory contents in the absence of power. Access to all RTC functions and the external RAM is the same as conventional bytewide SRAM. Data is maintained in the Watchdog Timekeeper by intelligent control circuitry which detects the status of V_CC and write protects both memory and timekeeping functions when V_CC is out of tolerance. Timekeeper information includes hundredths of seconds, seconds, minutes, hours, day, date, month, and year. The date at the end of the month is automatically adjusted for months with less than 31 days, including correction for leap year. The timekeeper operates in either 12- or 24-hour format with an AM/PM indicator. The watchdog internal timer DS1384 provides watchdog alarm windows and interval timing between 0.01 seconds and 99.99 seconds. The real time alarm provides for preset times of up to one week. All of the RTC functions and the internal 50 bytes of RAM reside in the lower 64 bytes of the attached RAM memory map. The externally attached static RAM is controlled by the DS1384 via the OER and CEO signals.

Automatic backup and write protection for an external SRAM is provided through the V_CCO, CEO and OER pins. The lithium energy source used to permanently power the real time clock is also used to retain RAM data in the absence of V_CC power through the V_CCO pin. The chip enable output to RAM ( CEO ) and the output enable to RAM ( OER ) are controlled during power transients to prevent data corruption. The DS1384 is a complete one-chip solution in that an external crystal and battery are the only components required to maintain time of day memory status in the absence of power.