Datasheet

D7 D6 D5 D4 D3 D2 D1 D0
1 9 1 9
Ack
by
LM95234
Start by
Master
R/W
Frame 1
Serial Bus Address Byte
Frame 2
Command Byte
Ack
by
LM95234
D7 D6 D5 D4 D3 D2 D1 D0
1 9
Frame 3
Data Byte
Ack by
LM95234
Stop
by
Master
SMBCLK
SMBDAT
SMBCLK
(Continued)
SMBDAT
(Continued)
A5 A3 A2 A0A6 A4 A1
LM95234
www.ti.com SNIS136D –AUGUST 2006–REVISED MARCH 2013
DIODE FAULT DETECTION
The LM95234 is equipped with operational circuitry designed to detect fault conditions concerning the remote
diodes. In the event that the D+ pin is detected as shorted to GND, D−, V
DD
or D+ is floating, the Remote
Temperature reading is –128.000 °C if signed format is selected and 0 °C if unsigned format is selected. In
addition, the appropriate status register bits RD1M or RD2M (D1 or D0) are set.
COMMUNICATING with the LM95234
The data registers in the LM95234 are selected by the Command Register. At power-up the Command Register
is set to “00”, the location for the Read Local Temperature Register. The Command Register latches the last
location it was set to. Each data register in the LM95234 falls into one of three types of user accessibility:
1. Read only
2. Write only
3. Write/Read same address
A Write to the LM95234 will always include the address byte and the command byte. A write to any register
requires one data byte.
Reading the LM95234 can take place either of two ways:
1. If the location latched in the Command Register is correct (most of the time it is expected that the Command
Register will point to one of the Read Temperature Registers because that will be the data most frequently
read from the LM95234), then the read can simply consist of an address byte, followed by retrieving the data
byte.
2. If the Command Register needs to be set, then an address byte, command byte, repeat start, and another
address byte will accomplish a read.
The data byte has the most significant bit first. At the end of a read, the LM95234 can accept either acknowledge
or No Acknowledge from the Master (No Acknowledge is typically used as a signal for the slave that the Master
has read its last byte). It takes the LM95234 190 ms (typical, all channels enabled) to measure the temperature
of the remote diodes and internal diode. When retrieving all 11 bits from a previous remote diode temperature
measurement, the master must insure that all 11 bits are from the same temperature conversion. This may be
achieved by reading the MSB register first. The LSB will be locked after the MSB is read. The LSB will be
unlocked after being read. If the user reads MSBs consecutively, each time the MSB is read, the LSB associated
with that temperature will be locked in and override the previous LSB value locked-in.
SMBus Timing Diagrams
Figure 19. Serial Bus Write to the internal Command Register followed by a the Data Byte
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