# Structure of a PKW telegram

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PNU: parameter number

AK: Request (Output buffer) or response identifier (Input buffer)

Table 1: Request identifier (master to slave)

Request identifier (AK) | Meaning | Response identifier (AK)
positive | negative
0 | No request | 0 | 7
1 | Request parameter value | 1 or 2 | 7
2 | Modify parameter value (word) | 1 | 7
3 | Modify parameter value (double word) | 2 | 7
6 | Request parameter value (array) | 4 or 5 | 7
7 | Modify parameter value (array, word) | 4 | 7
8 | Modify parameter value (array, double word) | 5 | 7
9 | Request number of array elements | 6 | 7

If the response identifier is „not possible to process request“ (value 7), there is an additional error code in the PWE (lower value, PWE2).

Table 2: Response identifier (valve to master)

Response identifier (AK) | Meaning
0 | No response
1 | Transfer parameter value (word)
2 | Transfer parameter value (double word)
4 | Transfer parameter value (array, word)
5 | Transfer parameter value (array, double word)
6 | Transfer number of array elements
7 | Not possible to process request (error code in PWE2)

Table 3: Error codes

Error code | Meaning
0 | Illegal parameter number (PNU)
1 | No access rights
2 | Value out of range
3 | Wrong array index
5 | Wrong data type (The request does not correspond to the data type of the parameter)
6 | Setting not allowed (can only be reset)
17 | Request cannot be processed due to operating state
20 | Wrong value within value range
201 | Unknown command