AT30TS75A_14 Datasheet, PDF (14/37 Pages) ATMEL Corporation – Digital Temperature Sensor

6. Registers
The AT30TS75A 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
Register
Pointer Register
Temperature Register
Configuration Register
T_LOW Limit Register
T_HIGH Limit Register
Address
n/a
00h
01h
02h
03h
Read/Write
W
R
R/W
R/W
R/W
Size
8-bit
16-bit
16-bit
16-bit
16-bit
Power-on Default
00h
0000h
0000h
4B00h (75C)
5000h (80C)
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 AT30TS75A, 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 AT30TS75A, 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.
14 AT30TS75A [DATASHEET]
Atmel-8839I-DTS-AT30TS75A-Datasheet_102014