SI7021-A20 Datasheet, PDF (26/36 Pages) Silicon Laboratories – IC HUMIDITY AND TEMPERATURE SENSOR

Si7021-A20
6. Control Registers
Table 14. Register Summary
Register
User Register 1
Bit 7
RES1
Bit 6
VDDS
Bit 5
RSVD
Bit 4
RSVD
Bit 3
RSVD
Bit 2
HTRE
Bit 1
RSVD
Bit 0
RES0
Heater Control
Register
RSVD
HEATER[3:0]
Notes:
1. Any register not listed here is reserved and must not be written. The result of a read operation on these bits is
undefined.
2. Except where noted, reserved register bits will always read back as “1,” and are not affected by write operations. For
future compatibiliy, it is recommended that prior to a write operation, registers should be read. Then the values read
from the RSVD bits should be written back unchanged during the write operation.
6.1. Register Descriptions
Register 1. User Register 1
Bit
D7
D6
Name
RES1
VDDS
Type
R/W
R
Reset Settings = 0011_1010
D5
RSVD
R/W
D4
D3
RSVD RSVD
R/W
D2
HTRE
R/W
D1
RSVD
R/W
D0
RES0
R/W
Bit
D7; D0
D6
D5, D4, D3
D2
D1
Name
RES[1:0]
VDDS
RSVD
HTRE
RSVD
Function
Measurement Resolution:
RH
00:
12 bit
01:
8 bit
10:
10 bit
11:
11 bit
Temp
14 bit
12 bit
13 bit
11 bit
V_DD Status:
0:
1:
V_DD OK
V_DD Low
The minimum recommended operating voltage is 1.9 V. A transi-
tion of the V_DD status bit from 0 to 1 indicates that V_DD is
between 1.8 V and 1.9 V. If the V_DD drops below 1.8 V, the
device will no longer operate correctly.
Reserved
1 = On-chip Heater Enable
0 = On-chip Heater Disable
Reserved
26
Rev. 1.1