Rainbow Electronics LM95221 - Manual (Page 11)

1.0 Functional Description
(Continued)
1.8 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 SMB-
DAT 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 communi-
cation. After the start the LM95221 will expect an SMBus
Address address byte.
1.9 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.
2.0 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
Register Summary
Name
Command
(Hex)
Power-On
Default Value
(Hex) Read/Write
# of used
bits Comments
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
LM95221
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