TMP117AIDRVT datasheet(21/50 Pages) TI2

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7.5.3.1.2 Serial Bus Address

To communicate with the TMP117, the master must first address slave devices through an address byte. The

address byte has seven address bits and a read-write (R/W) bit that indicates the intent of executing a read or

write operation.

The TMP117 features an address pin to allow up to four devices to be addressed on a single bus. Table 7-2

describes the pin logic levels used to properly connect up to four devices. x represents the read-write (R/ W) bit.

Table 7-2. Address Pin and Slave Addresses

DEVICE TWO-WIRE ADDRESS

ADD0 PIN CONNECTION

1001000x

Ground

1001001x

V+

1001010x

SDA

1001011x

SCL

7.5.3.1.3 Writing and Reading Operation

The user can write a register address to the pointer register to access a particular register on the TMP117. The

value for the pointer register is the first byte transferred after the slave address byte with the R/ W bit low. Every

write operation to the TMP117 requires a value for the pointer register.

When reading from the TMP117, the last value stored in the pointer register by a write operation is used to

determine which register is read during a read operation. To change the register pointer for a read operation,

a new value must be written to the pointer register. The user can issue an address byte with the R/ W bit low,

followed by the pointer register byte to write a new value for the pointer register. No additional data is required.

The master can then generate a START condition and send the slave address byte with the R/ W bit high to

initiate the read command. See Figure 7-10 for details of this sequence. If repeated reads from the same register

are desired, it is not necessary to send the pointer register bytes continuously because the TMP117 retains the

pointer register value until the value is changed by the next write operation.

7.5.3.1.4 Slave Mode Operations

The TMP117 can operate as a slave receiver or slave transmitter. As a slave device, the TMP117 never drives

the SCL line.

7.5.3.1.4.1 Slave Receiver Mode

The first byte transmitted by the master is the slave address with the R/W bit low. The TMP117 then

acknowledges reception of a valid address. The next byte transmitted by the master is the pointer register. The

TMP117 then acknowledges reception of the pointer register byte. The next byte(s) are written to the register

addressed by the pointer register. The TMP117 acknowledges reception of each data byte. The master can

terminate data transfer by generating a START or STOP condition.

7.5.3.1.4.2 Slave Transmitter Mode

The first byte transmitted by the master is the slave address with the R/W bit high. The slave acknowledges

reception of a valid slave address. The next byte is transmitted by the slave and is the most significant byte

of the register indicated by the pointer register. The master acknowledges reception of the data byte. The next

byte transmitted by the slave is the least significant byte. The master acknowledges reception of the data byte.

The master can terminate data transfer by generating a not-acknowledge on reception of any data byte or by

generating a START or STOP condition.

7.5.3.1.5 SMBus Alert Function

The TMP117 supports the SMBus alert function. When the ALERT pin is connected to an SMBus alert signal

and a master senses that an alert condition is present, the master can send out an SMBus ALERT command

(0001 1001) to the bus. If the ALERT pin is active, the device acknowledges the SMBus ALERT command

and responds by returning the slave address on the SDA line. The eighth bit (LSB) of the slave address byte

indicates if the alert condition is caused by the temperature exceeding T(HIGH) or falling below T(LOW). The LSB is

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TMP117

SNOSD82D – JUNE 2018 – REVISED SEPTEMBER 2022

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