Performance and Error Handling

In this chapter of the documentation, we would explain performance and timing requirements for UDS communication and how they are supposed to be handled by UDS entities.

CAN specific

ISO standards defines following time values on the network layer of UDS on CAN communication:

Diagnostic on CAN timings

Network layer time values (N_As, N_Ar, N_Bs, N_Br, N_Cs, N_Cr) present during UDS on CAN communication.

Note

The example uses segmented diagnostic message transmission as all CAN timings values can be presented there (all these times are applicable in this case). For unsegmented diagnostic message transmission though, the only applicable time parameter is N_As.

N_As

N_As is a time parameter related to transmission of any CAN Packet by a sender. It is measured from the beginning of the CAN Frame (that carries such CAN Packet) transmission till the reception of a confirmation that this CAN Frame was received by a receiver.

Timeout value:

1000 ms

Error handling:

If N_As timeout is exceeded, then the transmission of the diagnostic message shall be aborted.

Affected CAN Packets:

N_Ar

N_Ar is a time parameter related to transmission of any CAN Packet by a receiver. It is measured from the beginning of the CAN Frame (that carries such CAN Packet) transmission till the reception of a confirmation that this CAN Frame was received by a sender.

Timeout value:

1000 ms

Error handling:

If N_Ar timeout is exceeded, then the reception of the diagnostic message shall be aborted.

Affected CAN Packets:

N_Bs

N_Bs is a time parameter related to Flow Control (CAN Packet) reception by a sender. It is measured from the end of the last CAN Packet transmission (either transmitted First Frame, Consecutive Frame or received Flow Control), till the reception of Flow Control.

Timeout value:

1000 ms

Error handling:

If N_Bs timeout is exceeded, then the reception of the diagnostic message shall be aborted.

Affected CAN Packets:

N_Br

N_Br is a time parameter related to Flow Control (CAN Packet) transmission by a receiver. It is measured from the end of the last CAN Packet transmission (either received First Frame, Consecutive Frame or transmitted Flow Control), till the start of Flow Control transmission.

Performance requirement:

A receiving entity is obliged to transmit Flow Control packet before value of N_Br achieves maximal value threshold.

[N_Br] + [N_Ar] < 0.9 * [N_Bs timeout]
[N_Br max] = 900ms - [N_Ar]
Affected CAN Packets:

N_Cs

N_Cs is a time parameter related to Consecutive Frame (CAN Packet) transmission by a sender. It is measured from the end of the last CAN Packet transmission (either received Flow Control or transmitted Consecutive Frame), till the start of Consecutive Frame transmission.

Performance requirement:

A sending entity is obliged to transmit Consecutive Frame packet before value of N_Cs achieves maximal value threshold.

[N_Cs] + [N_As] < 0.9 * [N_Cr timeout]
[N_Cs max] = 900ms - [N_As]
Affected CAN Packets:

N_Cr

N_Cr is a time parameter related to Consecutive Frame (CAN Packet) reception by a receiver. It is measured from the end of the last CAN Packet transmission (either transmitted Flow Control or received Consecutive Frame), till the reception of Consecutive Frame.

Timeout value:

1000 ms

Error handling:

If N_Cr timeout is exceeded, then the reception of the diagnostic message shall be aborted.

Affected CAN Packets: