Datasheet
LM95221
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SNIS134B –MAY 2004–REVISED MARCH 2013
SERIAL INTERFACE RESET
In the event that the SMBus Master is RESET while the LM95221 is transmitting on the SMBDAT line, the
LM95221 must be returned to a known state in the communication protocol. This may be done in one of two
ways:
1. When SMBDAT is LOW, the LM95221 SMBus state machine resets to the SMBus idle state if either
SMBDAT or SMBCLK are held low for more than 35ms (t
TIMEOUT
). Note that according to SMBus
specification 2.0 all devices are to timeout when either the SMBCLK or SMBDAT lines are held low for 25-
35ms. Therefore, to insure a timeout of all devices on the bus the SMBCLK or SMBDAT lines must be held
low for at least 35ms.
2. When SMBDAT is HIGH, have the master initiate an SMBus start. The LM95221 will respond properly to an
SMBus start condition at any point during the communication. After the start the LM95221 will expect an
SMBus Address address byte.
ONE-SHOT CONVERSION
The One-Shot register is used to initiate a single conversion and comparison cycle when the device is in standby
mode, after which the device returns to standby. This is not a data register and it is the write operation that
causes the one-shot conversion. The data written to this address is irrelevant and is not stored. A zero will
always be read from this register.
LM95221 Registers
Command register selects which registers will be read from or written to. Data for this register should be
transmitted during the Command Byte of the SMBus write communication.
P7 P6 P5 P4 P3 P2 P1 P0
Command
P0-P7: Command
Table 3. Register Summary
Name Command Power-On Read/Write # of used bits Comments
(Hex) Default Value
(Hex)
Status Register 02h - RO 3 2 status bits and 1 busy bit
Configuration Register 03h 00h R/W 4 Includes conversion rate control
1-shot 0Fh - WO - Activates one conversion for all
3 channels if the chip is in
standby mode (i.e. RUN/STOP
bit = 1). Data transmitted by the
host is ignored by the LM95221.
Local Temperature MSB 10h - RO 8
Remote Temperature 1 MSB 11h - RO 8
Remote Temperature 2 MSB 12h - RO 8
Local Temperature LSB 20h - RO 2 All unused bits will report zero
Remote Temperature 1 LSB 21h - RO 3 All unused bits will report zero
Remote Temperature 2 LSB 22h - RO 3 All unused bits will report zero
Manufacturer ID FEh 01h RO
Revision ID FFh 61h RO
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