TMP112 datasheet(12/24 Pages) TI

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SLAVE MODE OPERATIONS

Slave Receiver Mode:

GENERAL CALL

HIGH-SPEED (Hs) MODE

Slave Transmitter Mode:

SMBus ALERT FUNCTION

TIMEOUT FUNCTION

TMP112

SBOS473B – MARCH 2009 – REVISED JUNE 2009 ......................................................................................................................................................... www.ti.com

reads from the same register are desired, it is not

For POL = '0', this bit is low if the temperature is

necessary to continually send the Pointer Register

greater than or equal to THIGH; this bit is high if the

bytes, because the TMP112 remembers the Pointer

temperature is less than TLOW. The polarity of this bit

is inverted if POL = '1'. Refer to Figure 18 for details

operation.

of this sequence.

Note that register bytes are sent with the most

If multiple devices on the bus respond to the SMBus

significant byte first, followed by the least significant

Alert command, arbitration during the slave address

byte.

portion of the SMBus Alert command determines

which device clears its ALERT status. The device

with the lowest two-wire address wins the arbitration.

If the TMP112 wins the arbitration, its ALERT pin

The TMP112 can operate as a slave receiver or slave

becomes inactive at the completion of the SMBus

transmitter. As a slave device, the TMP112 never

Alert command. If the TMP112 loses the arbitration,

drives the SCL line.

its ALERT pin remains active.

The first byte transmitted by the master is the slave

The TMP112 responds to a two-wire General Call

address, with the R/W bit low. The TMP112 then

address (0000000) if the eighth bit is '0'. The device

acknowledges reception of a valid address. The next

acknowledges

the

General

Call

address

and

byte transmitted by the master is the Pointer

responds to commands in the second byte. If the

second byte is 00000110, the TMP112 internal

of the Pointer Register byte. The next byte or bytes

registers are reset to power-up values. The TMP112

are written to the register addressed by the Pointer

does not support the General Address acquire

command.

each data byte. The master can terminate data

transfer by generating a START or STOP condition.

In order for the two-wire bus to operate at frequencies

above 400kHz, the master device must issue an

The first byte transmitted by the master is the slave

Hs-mode master code (00001xxx) as the first byte

address,

with

the

R/W

bit

high.

The

slave

after a START condition to switch the bus to

acknowledges reception of a valid slave address. The

high-speed

operation.

The

TMP112

does

not

next byte is transmitted by the slave and is the most

acknowledge this byte, but switches its input filters on

significant byte of the register indicated by the Pointer

SDA and SCL and its output filters on SDA to operate

in Hs-mode, allowing transfers at up to 3.4MHz. After

data byte. The next byte transmitted by the slave is

the Hs-mode master code has been issued, the

the least significant byte. The master acknowledges

master transmits a two-wire slave address to initiate a

reception of the data byte. The master can terminate

data transfer operation. The bus continues to operate

data transfer by generating a Not-Acknowledge on

in Hs-mode until a STOP condition occurs on the bus.

reception of any data byte, or generating a START or

Upon receiving the STOP condition, the TMP112

STOP condition.

switches

the

input

and

output

filters

back

fast-mode operation.

The TMP112 supports the SMBus Alert function.

When the TMP112 operates in Interrupt mode (TM =

The TMP112 resets the serial interface if SCL is held

'1'), the ALERT pin may be connected as an SMBus

low for 30ms (typ). The TMP112 releases the bus if it

Alert signal. When a master senses that an ALERT

is pulled low and waits for a START condition. To

condition is present on the ALERT line, the master

avoid activating the timeout function, it is necessary

sends an SMBus Alert command (00011001) to the

to maintain a communication speed of at least 1kHz

bus.

the

ALERT

active,

the

device

for SCL operating frequency.

acknowledges

the

SMBus

Alert

command

and

responds by returning its slave address on the SDA

line. The eighth bit (LSB) of the slave address byte

indicates if the ALERT condition was caused by the

temperature exceeding THIGH or falling below TLOW.

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