UM1915 Rev 3
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UM1915
STM8AF safety architecture
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configuration registers, detecting bit flips . The registers test is executed at least once per
DTI.
Protocol error signal - LINUART_SM_1
The LIN protocol errors signals (if used) despite being conceived to detect physical layer
related abnormal conditions, are able to contribute to the detection to faults leading to error
messages generation. For instance, option parity bit in data byte frame, overrun error.
Handling such error signals at application level is a common technique in embedded
applications.
Information redundancy techniques on messages - LINUART_SM_2
The redundant information technique is used to protect the LIN/UART communications by
detecting both the permanent and transient faults. There are two different approaches to
implement this technique:
•
multiple sending of the same message, with comparison of the received results
•
addition by the sender of a checksum field to the message to be verified by the
receiver.
In case the checksum field approach is adopted, the selection of the algorithm for
checksum computation ensures a similar protection against message corruption as that
ensured by a full redundancy. Theoretical demonstrations on coverage capability are
admitted, the use of CRC coding is anyway suggested.
The above reported approaches are equivalent; an additional criterion for the selection of
the approach is the availability of a quick hardware support on the MCU platform, and the
evaluation of the computation capability of the external device exchanging data with
STM8AF.
3.6.8 USART
Periodical read-back of configuration registers - UART_SM_0
This diagnostic measure, typically referred to as “Read back periodic by software of
configuration registers”, executes a periodical check of the configuration registers of
USART respect to their expected value (previously stored in RAM and adequately updated
after each configuration change). It mainly addresses transient faults affecting the
configuration registers, detecting bit flips. The registers test is executed at least once per
DTI.
Protocol error signals - UART_SM_1
The UART protocol errors signals (if used) are conceived to detect physical layer related
abnormal conditions, and are able to contribute to the detection of faults leading to error
messages generation (such as option parity bit in data byte frame, overrun error).
Handling such error signals at application level is a common technique in embedded
applications.