Figure 6. Two-wire Read Command Timing Diagram

When writing data to the TMP112B , after the slave address byte is sent, accessing a particular

register on the TMP112B is accomplished by writing the appropriate value to the pointer register. Every write

operation to the TMP112B requires a value for the pointer register.

When reading from the TMP112B

device, after the slave address byte is sent, the corresponding

pointer register byte also needs to be sent. Unlike the write operation, if the user need to repeatedly read data from

the same register, it is not required to send the pointer register byte separately each time, the last value stored in

the pointer register will be read by the device automatically; to change the register pointer for a read operation, a

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

with the R/W bit low, followed by the pointer register byte. 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.

Register bytes are sent with the MSB first, followed by the LSB. Figure 5 and Figure 6 show schematic diagrams

of the above read and write operations.

SMBus Alert Function

The TMP112B supports the SMBus alert function. When the TMP112B operates in interrupt mode (TM=1), the

master can send out and SMBus ALERT command (19h) to the bus. If the ALERT pin is active, the device

acknowledges

D7

D6

D5

D4

ACK by

Master

Frame 5 Data-Byte 2 Read Register

1

9

D3

D2

D1

D0

STOP By

Master

SCL

(Continued)

SDA

(Continued)

the SMBus ALERT command and responds by returning the slave address. The eighth bit (LSB) of the slave address

byte indicates if the alert condition is caused by the temperature exceeding THIGH or falling below TLOW. This bit is

equal to POL if the temperature is greater than or equal to THIGH; this bit is equal to POL if the temperature is less

than TLOW.

If multiple devices on the bus respond to the SMBus ALERT command, the bus will return the lowest two-wire

address. The TMP112B ALERT pin becomes inactive at the completion of the SMBus ALERT command; the

ALERT pin of the TMP112B that does not return an address will remain active. Sending the

SMBus ALERT command again can continue to clear the ALERT pin of the TMP112B with the current

lowest address. The above process is detailed in Figure 7.

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