TMP112ASLASHBSLASHN datasheet(18/47 Pages) TI1

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When reading from the TMP112 family, the last value stored in the pointer register by a write operation is used

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

new value must be written to the pointer register. This action is accomplished by issuing a slave-address byte

with the R/W bit low, followed by the pointer register byte. No additional data are 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 7-5 for details of this sequence. If repeated reads from the same register are desired, continuously

sending the pointer register bytes is not necessary because the TMP112 family retains the pointer register value

until the value is changed by the next write operation.

7.3.2.4 Slave Mode Operations

The TMP112 family can operate as a slave receiver or slave transmitter. As a slave device, the TMP112 family

never drives the SCL line.

7.3.2.4.1 Slave Receiver Mode

The first byte transmitted by the master is the slave address with the R/W bit low. The TMP112 family then

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

TMP112 family then acknowledges reception of the pointer register byte. The next byte or bytes are written to

the register addressed by the pointer register. The TMP112 family acknowledges reception of each data byte.

The master can terminate data transfer by generating a START or STOP condition.

7.3.2.4.2 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.

7.3.2.5 SMBus Alert Function

The TMP112 family supports the SMBus alert function. When the TMP112 family operates in interrupt mode (TM

= 1), the ALERT pin can be connected as an SMBus alert signal (when the ALERT pin is available). Irrespective

of the availability of the ALERT pin, the alert status is set. When a master senses that an alert condition is

present on the alert line, the master sends an SMBus ALERT command (0001 1001) to the bus. If the ALERT

pin is active or the alert is set, 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 high if the temperature is

greater than T(HIGH), or low if the temperature is less than T(LOW). Refer to the Figure 7-6 section for details of

this sequence.

If multiple devices on the bus respond to the SMBus ALERT command, arbitration during the slave address

portion of the SMBus ALERT command determines which device clears the alert status of that device. The

device with the lowest two-wire address wins the arbitration. If the TMP112 family wins the arbitration, the

TMP112 family ALERT pin becomes inactive and/or clears the status bit at the completion of the SMBus ALERT

command. If the TMP112 family loses the arbitration, the TMP112 family ALERT pin and/or the status bit remains

active.

7.3.2.6 General Call

The TMP112 family responds to a two-wire general-call address (0000 000) if the eighth bit is 0. The device

acknowledges the general-call address and responds to commands in the second byte. If the second byte is

0000 0110, the TMP112 family internal registers are reset to power-up values. The TMP112 family does not

support the general-address acquire command.

TMP112

SBOS473J – MARCH 2009 – REVISED FEBRUARY 2024

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