www.sensirion.com / D1

Version 1

– December 2022

15/26

4.9 Reset

A system reset of the SHT33-DIS can be generated externally by issuing a command (soft reset)

or by sending a pulse to the dedicated reset pin (nReset pin). Additionally, a system reset is

generated internally during power-up. During the reset procedure the sensor will not process

commands. In order to achieve a full reset of the sensor without removing the power supply, it is

recommended to use the nRESET pin of the SHT33-DIS.

Interface Reset

If communication with the device is lost, the following signal sequence will reset the serial interface:

While leaving SDA high, toggle SCL nine or more times. This must be followed by a Transmission

Start sequence preceding the next command. This sequence resets the interface only. The status

register preserves its content.

Soft Reset / Re-Initialization

The SHT33-DIS provides a soft reset mechanism that forces the system into a well-defined state

without removing the power supply. When the system is in idle state the soft reset command can

be sent to the SHT33-DIS. This triggers the sensor to reset its system controller and reloads

calibration data from the memory. In order to start the soft reset procedure the command as shown

in Table 15 should be sent. It is worth noting that the sensor reloads calibration data prior to every

measurement by default.

Command

Hex Code

Soft Reset

0x30A2

Table 15. Soft reset command (Clear blocks are controlled by the microcontroller, grey blocks by the sensor).

Reset through General Call

Additionally, a reset of the sensor can also be generated using the “general call” mode according

to I2C-bus specification14. This generates a reset which is functionally identical to using the nReset

pin. It is important to understand that a reset generated in this way is not device specific. All devices

on the same I2C bus that support the general call mode will perform a reset. Additionally, this

command only works when the sensor is able to process I2C commands. The appropriate

command consists of two bytes and is shown in Table 16.

Command

Code

Address byte

0x00

Second byte

0x06

Reset command using the

general call address

0x0006

Table 16. Reset through the general call address (Clear blocks are controlled by the microcontroller, grey

blocks by the sensor).

S General Call Address

1

2

3

4

5

6

7

8

9

Reset Command

1

2

3

4

5

6

7

8

9

General Call 1st byte

General Call 2nd byte