DS1615 Datasheet, PDF (15/24 Pages) Dallas Semiconductor – Temperature Recorder

DS1615
This register determines the low threshold for interrupt generation from the thermal sensor. If the
temperature is less than or equal to the value in this register, an inter-rupt will be activated if the
Temperature Low Interrupt Enable (TLIE) bit is set to a logic 1.
CURRENT TEMPERATURE REGISTER
MSb
LSb
CT7
CT6
CT5
CT4
CT3
CT2
CT1
CT0
This register provides the most recently acquired temperature measurement. It contains either the most
recently measured sample from automatic datalogging or it contains data that was acquired in response to
a users instruction for an immediate temperature measurement. An immediate measurement is acquired
by issuing the Read Temperature command.
After issuing the Read Temperature command, the value in this register is valid only if the Temperature
Ready (TR) bit in the Status register is a logic 1.
CURRENT SAMPLES COUNTER
This three-byte register set provides the number of samples that have been logged during the current data
logging operation (also known as a “mission”). The con-tents of this register can be used by software to
point to the most recent data sample in the Datalog NV RAM. The data in these registers are cleared by
enabling and issuing the Clear Memory command.
TOTAL SAMPLES COUNTER
This three-byte register set provides the total number of data samples that have been logged during the
life of the product. This value cannot be written by the end user. The value in this register is maintained
as long as the lithium energy source is available.
SILICON SERIAL NUMBER
A unique 64-bit lasered serial number is located in the register bank. This serial number is divided into
three parts. The first byte contains a model number (17h) to identify the device type. The next six
registers contain a unique binary number. The last serial number byte contains a CRC byte used to
validate the data in the first seven serial number registers. All eight bytes of the serial number are read
only registers.
The DS1615 is manufactured such that no two devices will contain an identical serial number. Blocks of
numbers can be reserved by the customer. Contact Dallas Semiconductor for special ordering
information for devices with reserved blocks of serial numbers.
SECURITY
The DS1615 provides several measures to insure data integrity for the end user. These security measures
are intended to prevent third party intermediaries from tampering with the data that has been stored in the
Datalog and Histogram memory.
As a first security measure, the Datalog and Histogram memory are Read-only from the perspective of the
end user. The DS1615 can write sampled data into these memory banks, but the end user cannot write
data to individual registers. This prevents an unscrupulous intermediary from writing false data to the
DS1615. The end user, however, can clear the contents of the Datalog and Histogram memory. This is
accomplished by enabling and issuing the Clear Memory command.
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