DS1689/DS1693

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DESCRIPTION

The DS1689/DS1693 is a real time clock (RTC) designed as a successor to the industry standard DS1285,

DS1385, DS1485, and DS1585 PC real time clocks. This device provides the industry standard DS1285

clock function with the new feature of either +3.0- or +5.0 volt 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 NVSRAM, 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 insure 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. Blocks

of available numbers from Dallas Semiconductor can be reserved by the customer.

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

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

shut down.

The DS1689/DS1693 incorporates 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 32.768 kHz 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.

SIGNAL DESCRIPTIONS

Five-volt operation is selected when the PSEL pin is at a logic 1. If PSEL is floated or at a logic 0, the

voltage level.

PSEL (Power Select Input) - This pin selects whether 3-volt operation or 5-volt operation will be used.

When PSEL is a logic 1, 5-volt operation is selected. When PSEL is a logic 0 or is floated, the device will