Datasheet

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 T
HIGH
; this bit is high if the
bytes, because the TMP112 remembers the Pointer temperature is less than T
LOW
. The polarity of this bit
Register value until it is changed by the next write 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
Register. The TMP112 then acknowledges reception
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
Register. The TMP112 acknowledges reception of
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
Register. The master acknowledges reception of the
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 to
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. If the ALERT pin is 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 T
HIGH
or falling below T
LOW
.
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