DS1689/DS1693

5 of 36

DETAILED DESCRIPTION

The DS1689/DS1693 are real-time clocks (RTCs) designed as successors to the industry standard

DS1285, DS1385, DS1485, and DS1585 PC real-time clocks. These devices provide the industry

standard DS1285 clock function with the new feature of either +3.0V or +5.0V operation and automatic

backup and write protection to an external SRAM. The DS1689 also incorporates a number of enhanced

features including a silicon serial number, power-on/off control circuitry, and 114 bytes of user NV

SRAM, power-on elapsed timer, and power-cycle counter.

Each DS1689/DS1693 is individually manufactured with a unique 64-bit serial number as well as an

additional 64-bit customer specific ROM or serial number. The serial number is programmed and tested

at Dallas to ensure that no two devices are alike. The serial number can be used to electronically identify

a system for purposes such as establishment of a network node address or for maintenance tracking.

Customers can reserve blocks of available numbers from Dallas Semiconductor.

The serialized RTCs also incorporate power control circuitry, which allows the system to be powered on

via an external stimulus, such as a keyboard or by a time and date (wake-up) alarm. The

PWR output pin

can be triggered by one or either of these events, and can be used to turn on an external power supply.

The

PWR pin is under software control, so that when a task is complete, the system power can then be

shut down.

The DS1689/DS1693 incorporate a power-on elapsed time counter, a power-on cycle counter, and a

battery powered continuous counter. These three counters provide valuable information for maintenance

and warranty requirements.

pins. The lithium energy source used to permanently power the real time clock is also used to retain RAM

controlled during power transients to prevent data corruption.

The DS1689 is a clock/calendar chip with the features described above. An external crystal and battery

are the only components required to maintain time-of-day and memory status in the absence of power.

The DS1693 incorporates the DS1689 chip, a 32.768kHz crystal, and a lithium battery in a complete, self-

contained timekeeping module. The entire unit is fully tested at Dallas Semiconductor such that a

OPERATION

The block diagram in Figure 1 shows the pin connections with the major internal functions of the

DS1689/DS1693. The following paragraphs describe the function of each pin.