www.sensirion.com Rev. 1.1 – October 2009 1/3
Electronic Identification Code
How to read-out the serial number of SHT2x
1 Communication Sequence
The communication sequences for reading out the serial number comply with the general I
2
C serial interface protocol.
For detailed information on I
2
C, please refer to the Datasheet SHT2x and the I
2
C bus specification by NXP
Semiconductors (http://www.standardics.nxp.com/support/i2c/).
The serial number of the SHT2x is partitioned to two different locations on the on-chip memory. Therefore, two memory
access sequences are required to retrieve the complete serial number information. Figure 1 shows the corresponding
communication sequence.
c
S I2CAdr
first memory access:
1 1 0 1 0
SNB_3
ACK
CRC
ACK
1 1 1W 0 1 1 1 10 0 0
S I2CAdr
ACK
R
SNB_2
ACK
CRC
ACK
ACK
ACK
SNB_1
ACK
CRC
ACK
SNB_0
ACK
CRC P
S I2CAdr
second memory access:
1 1 1 0 0
SNC_1
ACK
SNC_0
ACK
1 1 1W 0 1 0 0 11 1 0
S I2CAdr
ACK
R
CRC
ACK ACK
ACK
ACKACK
SNA_1
ACK
SNA_0
ACK
CRC P
S I2C start condition
P I2C stop condition
ACK
ACK
acknowledge by SHT2x acknowledge by master
normal font:
bold, italic font:
data direction master-to-SHT2x
data direction SHT2x-to-master
SDA
SDA
NACK
not-acknowledge by master
NACK
NACK
Figure 1: Communication sequences.
The SHT2x provides a device specific serial number which can be read
-
out via the serial interface (I
2
C) and allow
s for an
unambiguous identification of each individual device. This application note describes the procedure for read-out of the
serial number.
