AT30TS75 [DATASHEET]
Atmel-8748E-DTS-AT30TS75-Datasheet_092013
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6. Registers
The AT30TS75 contains five registers (a Pointer Register and four data registers) that are used to control the operational
mode and performance of the temperature sensor, store the user-defined high and low temperature limits, and store the
digitized temperature measurements. All accesses to the device are performed using these five registers. In order to
read from and write to one of the device's four data registers, the user must first select a desired data register by utilizing
the Pointer Register.
Table 6-1. Registers
The Configuration Register, despite being 16-bits wide, is compatible to industry standard LM75-type temperature
sensors that use an 8-bit wide register in that only the first 8-bits of the Configuration Register need to be written to or
read from.
6.1 Pointer Register
The 8-bit Write-only Pointer Register is used to address and select which one of the device's four data registers
(Temperature Register, Configuration Register, T
LOW
Limit Register, or T
HIGH
Limit Register) will be read from or written
to.
For Read operations from the AT30TS75, once the Pointer Register is set to point to a particular data register, it remains
pointed to that same data register until the Pointer Register value is changed.
Example: If the user sets the Pointer Register to point to the Temperature Register, then all subsequent reads from
the device will output data from the Temperature Register until the Pointer Register value is changed.
For Write operations to the AT30TS75, the Pointer Register value must be refreshed each time a Write to the device is to
be performed, even if the same data register is going to be written to a second time in a row.
Example: If the Pointer Register is set to point to the Configuration Register, once the subsequent Write operation to
the Configuration Register has completed, the user cannot write again into the Configuration Register
without first setting the Pointer Register value again. As long as a Write operation is to be performed, the
device will assume that the Pointer Register value is the first data byte received after the address byte.
Since only four data registers are available for access, only the two LSBs (P1 and P0) of the Pointer Register are used;
the remaining six bits (P7-P2) of the Pointer Register should always be set to zero to allow for future migration paths to
other temperature sensor devices that have more than four data registers. Table 6-2 shows the bit assignments of the
Pointer Register and the associated pointer addresses of the data registers available. Attempts to write any values other
than those listed in Table 6-2 into the Pointer Register will be ignored by the device, and the contents of the Pointer
Register will not be changed. However, the device will respond back to the Master with an ACK to indicate that the
device successfully received a data byte even though no operation will be performed.
Register Address Read/Write Size Power-On Default
Pointer Register n/a W 8-bit 00h
Temperature Register 00h R 16-bit 0000h
Configuration Register 01h R/W 16-bit 0000h
T
LOW
Limit Register 02h R/W 16-bit 4B00h (75qC)
T
HIGH
Limit Register 03h R/W 16-bit 5000h (80qC)
