SI7013 Datasheet, PDF (22/43 Pages) Silicon Laboratories – I2C HUMIDITY AND TWO-ZONE TEMPERATURE SENSOR

Si7013
5.1. Issuing a Measurement Command
The measurement commands instruct the Si7013 to perform one of four possible measurements; Relative
Humidity, Temperature, Auxiliary Temperature, or Analog Voltage. The procedure to issue any one of these
commands is identical. While the measurement is in progress, the option of either clock stretching (Hold Master
Mode) or Not Acknowledging read requests (No Hold Master Mode) is available to indicate to the master that the
measurement is in progress; the chosen command code determines which mode is used.
Optionally, a checksum byte can be returned from the slave for use in checking for transmission errors. The
checksum byte will follow the least significant measurement byte if it is acknowledged by the master. The
checksum byte is not returned if the master “not acknowledges” the least significant measurement byte. The
checksum byte is calculated using a CRC generator polynomial of x⁸ + x⁵ + x⁴ + 1 with an initialization of 0x00.
Master
Slave
Sequence to perform a measurement and read back result (Hold Master Mode)
Slave
S
W
Address
Measure
A
A
Cmd
Slave
Sr
R
Address
Clock
stretch
A
during ‐>
measure‐
ment
MS Byte
A
LS Byte
NA
P
A
Checksum
NA
P
Sequence to perform a measurement and read back result (No Hold Master Mode)
Slave
Measure
Slave
Slave
S
W
A
A
Sr
R
NA Slave Address R NA
Address
Cmd
Address
Address
R
A
MS Byte
A
LS Byte
NA
P A Checksum NA P
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Rev. 0.95