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8.11.2.2 Request Message Data Parameter Definitions (Table 125).
Table 125: Request Message Data Parameter Definition
Definition
parameterIdentifier
The parameterIdentifier is a 2-byte number assigned to individual diagnostic signals or parameters. The
parameterIdentifier (PID) number is used by the $2C service to build dynamic DPIDs or the $22 service to
request specific diagnostic parameters
memoryAddress
The parameter memoryAddress is used to select the starting address of ECU memory from which data is to be
retrieved. A portion of the memoryAddress parameter (most significant bits or bytes) can be used as a
memoryIdentifier.
An example of the use of a memoryIdentifier would be a dual processor ECU with 16-bit addressing and
memory address overlap (when a given address is valid for either processor but yields a different physical
memory device). In this case, a 3-byte memoryAddress parameter can be specified and the most significant
byte of the memoryAddress parameter could then be used to select which physical memory device the tester is
attempting to retrieve data from. Any usage of a memoryIdentifier shall be documented in the appropriate CTS,
SSTS or supplemental diagnostic specification referenced by the CTS or SSTS.
memorySize
The parameter memorySize is used to select the number of consecutive memory addresses (in ascending
order) to be read starting at memoryAddress (memorySize includes the starting location). MemorySize shall
have a value between one and seven bytes. The maximum value comes from the maximum number of bytes
allowed in a UUDT diagnostic response (of the $AA service).
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WORLDWIDE ENGINEERING STANDARDS General Motors Local Area Network Enhanced Diagnostic Test Mode Specification
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