Datasheet STTS22H (STMicroelectronics) - 9

STTS22H SMBus interface 5.1.3 READ byte
The READ byte protocol is used to read one byte of data from the registers as shown in the following table.
Table 7. SMBus READ protocol Slave Register Slave Start WR ACK ACK start RD ACK data NACK stop address address address
1 bit 7 bits 1 bit 1 bit 8 bits 1 bit 8 bits 1 bit 1 bit
5.1.4 SEND byte
The SEND byte protocol is used to set the internal address register to the correct address. It sends a register address with no data (see following table). The SEND byte can be followed by the RECEIVE byte protocol described in the following section in order to read data from the register
Table 8. SMBus SEND protocol Slave Register Start WR ACK ACK stop address address
1 bit 7 bits 1 bit 1 bit 8 bits 1 bit 1 bit
5.1.5 RECEIVE byte
The RECEIVE byte protocol is used to read data from the register when the internal register address pointer is known (see following table). This can be used for consecutive reads of the same register.
Table 9. SMBus RECEIVE protocol Slave Start RD ACK data NACK stop address
1 bit 7 bits 1 bit 1 bit 8 bits 1 bit 1 bit
5.1.6 SMBus timeout
The STTS22H supports SMBus timeout which is enabled by default at power-up. This can be disabled via bit 1 in the CTRL register. When timeout is enabled, the STTS22H will time out after 30 ms (typ) of inactivity. The STTS22H supports the SMBus timeout feature. If the host holds SCL low for more than tTIMEOUT (max), the STTS22H resets and releases the bus. This feature is turned on by default.
5.1.7 Alert response address
The STTS22H supports the SMBus alert response address (ARA) protocol. In the event of an out-of-limit temperature measurement, the ALERT / INT output will be asserted. In response, the host (supporting the ARA protocol) will send the SMBus Alert Response Address to the general (slave) address of 0001_100b. All devices with active interrupts will respond with their client addresses (with the LSB bit set to 0). The STTS22H will acknowledge the ARA and respond with its slave device address. ARA transfer details are available in the following table.
Table 10. ARA transfer details Alert response STTS22H slave Start RD ACK NACK Stop address address
1 bit 7 bit 1 bit 1 bit 8 bit 1 bit 1 bit
DS12606
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Rev 4 page 9/29
Document Outline 1 Overview 2 Pin description 3 Sensor parameters and electrical specifications 3.1 Sensor accuracy specifications 4 Absolute maximum ratings 5 Digital interfaces 5.1 SMBus interface 5.1.1 SMBus protocol 5.1.2 WRITE byte 5.1.3 READ byte 5.1.4 SEND byte 5.1.5 RECEIVE byte 5.1.6 SMBus timeout 5.1.7 Alert response address 5.2 I²C interface 5.2.1 I²C protocol 5.2.2 I²C read and write sequences 6 Register description 6.1 WHOAMI (01h) - RO 6.2 TEMP_H_LIMIT (02h) - RW 6.3 TEMP_L_LIMIT (03h) - RW 6.4 CTRL (04h) - RW 6.5 STATUS (05h) - RO 6.6 TEMP_L_OUT (06h) - RO 6.7 TEMP_H_OUT (07h) - RO 6.8 SOFTWARE_RESET (0Ch) - RW 7 Interrupt 8 ALERT / INT output 9 Operating modes 9.1 Enable sequence for one-shot mode 9.2 Enable sequence for freerun mode 9.3 Enable sequence for low-ODR mode 10 Package information 10.1 Soldering information 10.2 UDFN-6L package information 10.3 UDFN-6L packing information Revision history