SM CODE IIC_SM_2
Detailed implementation
This method is implemented adding to data packets transferred by I2C a redundancy check (like a CRC
check, or similar one) with encoding capability. The checksum encoding capability must be robust
enough to guarantee at least 90% probability of detection for a single bit flip in the data packet.
Consistency of data packet must be checked by the application software before consuming data
Error reporting Depends on implementation
Fault detection time Depends on implementation
Addressed fault model Permanent and Transient
Dependency on MCU configuration None
Initialization Depends on implementation
Periodicity On demand
Test for the diagnostic Not needed
Multiple faults protection CPU_SM_0: periodical core self-test software
Recommendations and known
limitations
It is assumed that the remote I2C counterpart has an equivalent capability of performing the check
described.
Transmission full redundancy (message repetition) should not be used because its detection capability is
limited to a subset of communication unit failure modes.
To give an example on checksum encoding capability, using just a bit-by-bit addition is unappropriated.
This method is superseded by IIC_SM_3 if hardware handled CRC insertion is possible
Table 47. IIC_SM_3
SM CODE IIC_SM_3
Description CRC packet-level
Ownership ST
Detailed implementation
I2C communication module allows to activate for specific mode of operation (SMBus) the automatic
insertion (and check) of CRC checksums to packet data.
Error reporting Error flag raise and optional Interrupt Event generation
Fault detection time Depends on peripheral configuration (e.g. baud rate), refer to functional documentation
Addressed fault model Permanent and Transient
Dependency on MCU configuration None
Initialization Depends on implementation
Periodicity Continuous
Test for the diagnostic Not needed
Multiple faults protection IIC_SM_2: Information redundancy techniques on messages
Recommendations and known limitations None
Table 48. IIC_SM_4
SM CODE IIC_SM_4
Description Information redundancy techniques on messages, including end-to-end safing
Ownership End user
Detailed implementation
This method aims to protect the communication between a I2C peripheral and his external
counterpart.
Refer to CAN_SM_2 description for detailed information.
UM1845
Description of hardware and software diagnostics
UM1845 - Rev 4
page 37/108
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