![[DoCAN] Vehicle Diagnostic Communication Part 60 [UDS 21]](https://www.simulationroom999.com/blog/wp-content/uploads/2022/12/01_eyecatch-22.png)
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https://www.simulationroom999.com/blog/diagnostic-communication-en-back-issue/
Introduction.
Explanation of ISO 14229, UDS.
This article explains the messages of the WriteDataByIdentifier service.
Request message for WriteDataByIdentifier service
Since the last article explained the usage scenario of the WriteDataByIdentifier service, this article will explain the messages.
The request message for the WriteDataByIdentifier service is as follows.
| Position | Parameter Name | Value |
|---|---|---|
| 1 | WriteDataByIdentifier Request SID | 0x2E |
| 2～3 | dataIdentifier | 0x0000-0xFFFF |
| 4～n | dataRecord | – |
While it was like multiple DIDs were lined up for the ReadDataByIdentifier service, only one DID is specified for the WriteDataByIdentifier service.
Unlike read, it is dangerous to write to an unexpected DID due to a specification error or misinterpretation of the DID, so I think this specification is designed to take care of that.
Not sure what would happen if there is a misinterpretation of Length by DID.
(Very dangerous!)
Response message for WriteDataByIdentifier service
The response message for the WriteDataByIdentifier service is as follows.
| Position | Parameter Name | Value |
|---|---|---|
| 1 | WriteDataByIdentifier Response SID | 0x6E |
| 2-3 | dataIdentifier | 0x0000-0xFFFF |
It is very simple, partly because one DID is fixed.
As for the meaning of the response message, it only means ” OK, it was written.
However, as explained in the last article, there is a possibility that NRC$78 may be included, so the actual communication may be complicated.
I have not yet decided whether or not to simulate the actual communication, including that part.
It should be possible, but if it seems too much trouble, I may decide not to do it.
( I will make an effort…)
Conclusion
- Explanation of the request message for the WriteDataByIdentifier service.
- Unlike the ReadDataByIdentifier service, one DID is fixed.
- Explanation of the response message of the WriteDataByIdentifier service.
- In practice, NRC$78 may be interleaved.
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