LM95231_06 NSC [National Semiconductor], LM95231_06 Datasheet - Page 11

• Manufacturer Part Number: LM95231_06
• Description: Precision Dual Remote Diode Temperature Sensor with SMBus Interface and TruTherm Technology
• Manufacturer: NSC [National Semiconductor]

1.0 Functional Description
1.7 COMMUNICATING with the LM95231
The data registers in the LM95231 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 LM95231 falls into one
of four types of user accessibility:
1. Read only
2. Write only
3. Write/Read same address
4. Write/Read different address
A Write to the LM95231 will always include the address byte
and the command byte. A write to any register requires one
data byte.
Reading the LM95231 can take place either of two ways:
1. If the location latched in the Command Register is cor-
rect (most of the time it is expected that the Command
(Continued)
11
2. If the Command Register needs to be set, then an
The data byte has the most significant bit first. At the end of
a read, the LM95231 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). 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 consecu-
tively, each time the MSB is read, the LSB associated with
that temperature will be locked in and override the previous
LSB value locked-in.
Register will point to one of the Read Temperature Reg-
isters because that will be the data most frequently read
from the LM95231), then the read can simply consist of
an address byte, followed by retrieving the data byte.
address byte, command byte, repeat start, and another
address byte will accomplish a read.
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