Data Transmission functional unit
The second type of diagnostic service of UDS: data transmission. This type of service includes the SID as follows:

ReadDataByIdentifier (0x22)
ReadMemoryByAddress (0x23)
ReadScalingDataByIdentifier (0x24)
ReadDataByPeriodicIdentifier (0x2A)
DynamicallyDefineDataIdentifier (0x2C)
WriteDataByIdentifier (0x2E)
WriteMemoryByAddress (0x3D)

Usually, 0x22 and 0x2E are used in pairs, and 0x23 and 0x3D are used in pairs. These services are used for basic read and write operations of diagnostic data. 0x24, 0x2A, 0x2C are some special operations. I have only used SIDs: 0x22 and 0x2E. At present, this chapter only introduces these two services. If there are other SIDs in the future, they will be added.

1. ReadDataByIdentifier (0x22) service

This service reads ECU data through identifiers.

1.1 Request format:

From the above figure, it can be seen that the request format is divided into two parts:
The first part: request SID: 0x22, occupy one word
The second part: dataIdentifier (DID), which occupies two bytes. The value of DID is defined by the manufacturer, which represents what data is read. For example, 0x0123 means to read the ECU version number. One request can read multiple DID data. The DID range is shown in the figure below:

1.2 Response format:

From the above figure, the response format can be divided into three parts:
The first part: response SID: 0x62
The second part: dataIdentifier (DID), the DID value requested to be read
The third part: dataRecord, to read the data corresponding to the DID.
Note: According to the number of DIDs requested by the diagnostic tool at one time, the ECU will respond to the diagnostic tool with the data of the number of DIDs. Format: response SID + n (dataIdentifier + dataRecore). Generally request to read one DID data at a time

1.3 Examples

Read the ECU version number, assuming DID: 0x0123 is the identifier of the ECU version number

2. WriteDataByIdentifier (0x2E) service

This service writes data to the ECU through an identifier.

2.1 Request format

As can be seen from the above figure, the request format is divided into three parts
The first part: request SID: 0x2E, occupying one byte
The second part: dataIdentifier (DID), need to write the corresponding DID identifier value of the data. Occupies two bytes
The third part: dataRecord, the data to be written

2.2 Response format

As can be seen from the above figure, the response format is divided into two parts
The first part: response SID: 0x6E
The second part: dataIdentifier (DID), request echo of DID

2.3 Examples
Write the ECU version number, assuming DID: 0x0123 is the identifier of the ECU version number

Know the parameters: https://zhuanlan.zhihu.com/p/33995635