STTS2004 datasheet(14/58 Pages) STMICROELECTRONICS

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Temperature sensor operation

STTS2004

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DocID024229 Rev 3

Temperature sensor operation

The temperature sensor continuously monitors the ambient temperature and updates the

temperature data register. Temperature data is latched internally by the device and may be

read by software from the bus host at any time.

The I2C slave address selection pins allow up to 8 such devices to co-exist on the same

bus. This means that up to 8 memory modules can be supported, given that each module

has one such slave device address slot.

After initial power-on, the configuration registers are set to the default values. The software

can write to the configuration register to set bits per the bit definitions in Section 3.1: I2C

communications.

For details of operation and usage of 4 Kb SPD EEPROM, refer to Section 5: SPD

EEPROM operation.

3.1

I2C communications

The registers in this device are selected by the pointer register. At power-up, the pointer

the last location it was set to. Each data register falls into one of three types of user

accessibility:

Read-only

Write-only, and

WRITE/READ same address

A WRITE to this device will always include the address byte and the pointer byte. A WRITE

to any register other than the pointer register, requires two data bytes.

Reading this device is achieved in one of two ways:



If the location latched in the pointer register is correct (most of the time it is expected

that the pointer register will point to one of the read temperature registers because that

will be the data most frequently read), then the READ can simply consist of an address

byte, followed by retrieval of the two data bytes.



If the pointer register needs to be set, then an address byte, pointer byte, repeat start,

and another address byte will accomplish a READ.

The data byte transfers the MSB first. At the end of a READ, this device can accept either

an acknowledge (ACK) or no acknowledge (No ACK) status from the master. The No ACK

status is typically used as a signal for the slave that the master has read its last byte. This

device subsequently takes up to 125 ms (max), 70 ms (typ) to measure the temperature for

the default temperature resolution.

Note:

The STTS2004 does not initiate clock stretching which is an optional I2C bus feature.

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