SI7021-A20 Datasheet, PDF (18/36 Pages) Silicon Laboratories – IC HUMIDITY AND TEMPERATURE SENSOR

Si7021-A20
5. I²C Interface
The Si7021 communicates with the host controller over a digital I²C interface. The 7-bit base slave address is
0x40.
Table 10. I²C Slave Address Byte
A6
A5
A4
A3
A2
A1
A0
R/W
1
0
0
0
0
0
0
0
Master I²C devices communicate with the Si7021 using a command structure. The commands are listed in the I²C
command table. Commands other than those documented below are undefined and should not be sent to the
device.
Table 11. I²C Command Table
Command Description
Measure Relative Humidity, Hold Master Mode
Measure Relative Humidity, No Hold Master Mode
Measure Temperature, Hold Master Mode
Measure Temperature, No Hold Master Mode
Read Temperature Value from Previous RH Measurement
Reset
Write RH/T User Register 1
Read RH/T User Register 1
Write Heater Control Register
Read Heater Control Register
Read Electronic ID 1st Byte
Read Electronic ID 2nd Byte
Read Firmware Revision
Command Code
0xE5
0xF5
0xE3
0xF3
0xE0
0xFE
0xE6
0xE7
0x51
0x11
0xFA 0x0F
0xFC 0xC9
0x84 0xB8
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Rev. 1.1