[RQ7.16] SPDU_ID_1, SPDU_ID_2 and SPDU_ID_3 shall be calculated according to Figure 19 and Table 36.
Figure 19 – Calculation of the SPDU_ID
Table 36 – Presentation of the SPDU_ID
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SPDU_ID_1 := SafetyBaseID (bytes 0…3) XOR SafetyProviderLevel_ID (bytes 0…3) |
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SPDU_ID_2 := SafetyBaseID (bytes 4…7) XOR SafetyStructureSignature (bytes 0…3) |
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SPDU_ID_3 := SafetyBaseID (bytes 8…11) XOR SafetyBaseID (bytes 12…15) XOR SafetyProviderID (bytes 0…3) |
In case of a mismatch between expected SPDU_ID and actual SPDU_ID, the following rules can be used for diagnostic purposes:
- If all of SPDU_ID1, SPDU_ID2, and SPDU_ID3 differ, there probably is a mismatching SafetyBaseID.
- If SPDU_ID3 differs, but SPDU_ID1 and SPDU_ID2 do not, there is a mismatching SafetyProviderID.
- If SPDU_ID2 differs, but SPDU_ID1 and SPDU_ID3 do not, the structure or identifier of the safety data do not match.
- If SPDU_ID1 differs, but SPDU_ID2 and SPDU_ID3 do not, the SafetyProviderLevel does not match.
By these rules, there is a very low probability (<10-9) that a mismatching SafetyBaseID will be misinterpreted. From a practical view, this probability can be ignored.