General

AUTOSAR COM plays a connecting role in the entire COM STACK COMPOENT, and is mainly responsible for sending and receiving data interactively with APPLICATION and IF. The specific content will be analyzed later

 

It consists of Signal/Signal Group/PDU and other information, whether it is LIN/CAN/FR application messages will eventually be mapped to COM Layer, that is to say, there is only the concept of Signal/Signal Group/PDU in COM Layer, and it will not pay attention to its By what method is it transmitted (LIN/CAN/FR)

 

Transmission Process

Transmission of a Signal

Send a SIGNAL via Com_SendSignal request

Com_SendSignal just updates the value to COM Buffer, and Com_MainFunctionTx will actually start the process of sending data to CAN BUS, so the call cycle of Com_MainFunctionTx determines the sending delay of TX message

 

CAN Write Process

Transmission of a Signal Group

Signal GroupThe role of is to be able to have a strong associationsignalassigned to aGroupmiddle, in aSignal Group ofSIGNAL no matter sendor receive as a whole

Com_SendSignal (GroupSignal1, &SigBuffer1);

Com_SendSignal (GroupSignal2, &SigBuffer2);

Com_SendSignalGroup (SignalGroupA); 、

For Signal Group, when Com_SendSignal is called, Value will be temporarily put into shadow Buffer, and when Com_SendSignalGroup is called, the content stored in shadow Buffer will be updated to COM Buffer together, thus achieving the effect of synchronous update

Confirmation of Transmission

 

IMMEDIATE

Com_TxConfirmation is triggered by Can_MainFunction_Write

DEFERRED

Com_TxConfirmation is triggered by Com_MainFunctionTx, because the period of Can_MainFunction_Write is often shorter than that of Com_TxConfirmation, so it can be considered that the delay of DEFERRED is greater than that of IMMEDIATE. If the period of the two is the same, there will be no change

Transmission Deadline Monitoring

Com Layer provides a Transmission Timeout mechanism to monitor whether the transmitted message is received within the specified time

The calculation method is from sending the COM trigger (Com_SendSignal / Com_TriggerIPduSend /cyclic triggers) to receiving the corresponding Confirmation

A scheduled Timeout Callback is executed when the timeout expires

Transmission Mode Selector

Transmission Mode

Divided into ComTxModeTrue and ComTxModeFalse two Modes

Each transmission mode includes two types of message transmission, namely Cycle and Event. When the result of transmission mode arbitration Rule is TRUE, the transmission mode will enter TRUE Mode, and report according to the message transmission type defined under TRUE Mode. Otherwise, it will enter FALSE Mode, and send messages according to the message sending type defined under FALSE Mode

For the Event message sending type, it should be emphasized that only the Triggered or Triggered On Change attribute is included in the ComTransferProperty configuration, the Event message sending will be triggered

Transmission Trigger

For messages containing Event sending types (MIXED, DIRECT), it should be emphasized that only when the ComTransferProperty configuration contains the Triggered or Triggered On Change attribute, the sending of Event messages will be triggered

It can be set separately for signal Group or signal, mainly divided into the following 4 attributes.

Pending

Triggered

Triggered on Change

None

Signal Group Transfer Property

Signal Transfer Property

Transmission mode Arbitrament Rule

At the Signal Level, the following expressions can be defined for each Signal. When one of the expressions contained in the PDU is true, then Transmission Mode Switch to True. When all the evaluation results of the signals are False, then Transmission Mode Switch to False

F_Always (TRUE)

F_Never (FALSE)

F_MaskedNewDiffersMaskedOld ((new_value&mask) != (old_value&mask))

F_MaskedNewEqualsX ((new_value&mask) == x)

F_MaskedNewDiffersX ((new_value&mask) != x)

F_MaskedNewIsOutside ((new_value<min) || (max<new_value))

F_MaskedNewIsWithin ((min<=new_value) && (new_value<=max))

You can also perform transmission Mode conversion by calling the Com_SwitchIpduTxMode API displayed

Minimum Send Distance of an I-PDU

MDT: The shortest time interval before any two frame messages with the same Frame ID

If ComEnableMDTForCyclicTransmission =false, then MDT only considers transmissions of type EVENT