SNIP_CLASSIC_COM_SECTION_4_3_1_11_2_Atomicity

4.3.1.11.2 Atomicity [SWS_Rte_04527] Upstream requirements: SRS_Rte_00019, SRS_Rte_00073, SRS_Rte_00091 ⌈The RTE shall treat AUTOSAR signals received and transmitted using sender-receiver communication atomically [SRS_Rte_00073].⌋ The RTE decomposes the composite data type into single signals as described above and passes them to the COM module by using the COM API call Com_SendSignal. As this set of single signals has to be treated as atomic, it is placed in a “signal group”. A signal group has to be placed always in a single I-PDU. Thus, atomicity is established. When all signals have been updated, the RTE initiates transmission of the signal group by using the COM API call Com_SendSignalGroup. As would be expected, the receiver side is the exact reverse of the transmission side: the RTE must first call Com_ReceiveSignalGroup precisely once for the signal group and then call Com_ReceiveSignal to extract the value of each signal within the signal group. A signal group has the additional property that COM guarantees to inform the receiver by invoking a call-back about its arrival only after all signals belonging to the signal group have been unpacked into a buffer. The Data Transformation approach is described in section 4.10.