DS1689_05 Datasheet, PDF (18/36 Pages) Dallas Semiconductor – 3V/5V Serialized Real-Time Clocks with NV RAM Control

DS1689/DS1693
SILICON SERIAL NUMBER/CUSTOMER SPECIFIC ROM
A total of 128 bits are available for use as serial number/ROM. These bits can be used as a 128-bit serial
number or as a unique 64-bit serial number and 64-bit customer specific serial number or ROM. The
unique 64-bit serial number is located in bank 1 registers 40H–47H. This serial number is divided into
three parts. The first byte in register 40H contains a model number to identify the device type and
revision of the DS1689/DS1693. Registers 41H–46H contain a unique binary number. Register 47H
contains a CRC byte used to validate the data in registers 40H–46H. The method used to create the CRC
byte is proprietary to Dallas Semiconductor, but can be made available if required. Typical applications
should consider this byte simply as part of the overall unique serial number. All 8 bytes of the serial
number are read-only registers.
The DS1689/DS1693 are manufactured such that no two devices contain an identical number in locations
41H–47H. Customers can reserve blocks of numbers for these locations. Contact Dallas Semiconductor
for special ordering information for DS1689/DS1693 with reserved blocks of serial numbers.
As already mentioned, another 64 bits are available for use as an additional serial number or customer
specific ROM. These 64 bits are located in bank 1 registers 60H–67H.
CENTURY COUNTER
A register has been added in bank 1, location 48H, to keep track of centuries. The value is read in either
binary or BCD according to the setting of the DM bit.
AUXILIARY BATTERY
The V_BAUX input is provided to supply power from an auxiliary battery for the DS1689/DS1693 kickstart,
wake-up, and SQW output features in the absence of V_CC. This power source must be available in order to
use these auxiliary features when no V_CC is applied to the device.
The auxiliary battery enable (ABE; bank 1, register 04BH) bit in extended Control Register B is used to
turn on and off the auxiliary battery for the above functions in the absence of V_CC. When set to a 1, V_BAUX
battery power is enabled, and when cleared to 0, V_BAUX battery power is disabled to these functions.
In the DS1689/DS1693, this auxiliary battery can be used as the primary backup power source for
maintaining the clock/calendar, user RAM, and extended external RAM functions. This occurs if the
V_BAT pin is at a lower voltage than V_BAUX. If the DS1689 is to be backed up using a single battery with
the auxiliary features enabled, then V_BAUX should be used and connected to V_BAT. If V_BAUX is not to be
used, it should be grounded and ABE should be cleared to 0.
WAKE-UP/KICKSTART
The DS1689/DS1693 incorporate a wake-up feature, which can power the system on at a predetermined
date through activation of the PWR output pin. In addition, the kickstart feature can allow the system to
be powered-up in response to a low-going transition on the KS pin, without operating voltage applied to
the V_CC pin. As a result, system power can be applied upon such events as a key closure, or modem ring
detect signal. To use either the wake-up or the kickstart features, the DS1689/DS1693 must have an
auxiliary battery connected to the V_BAUX pin, and the oscillator must be running and the countdown chain
must not be in reset (Register A DV2, DV1, DV0 = 01X). If DV2, DV1, and DV0 are not in this required
state, the PWR pin is not driven low in response to a kickstart or wakeup condition, while in battery-
backed mode.
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