Interpreters Document

KWP2000 Response Processing
 
Supported By:
KWP2000 Interpreter 2
 
 
Description: 
If a ECU doesn't respond (timeout) then No Communication Processing applies. 
If a negative response is received, then the tool searches for the response code (byte 3) of the received 
negative response in the goto fields and if found flags the appropriate step to execute next. 
In all other cases, the tool searches for the positive response service ID in the goto fields. 
 
When an Op-Code refers to the response buffer the bytes are identified as follows: 
Positive Response: 
Response 
Byte 
Value 
Byte Description 
1 
XX 
Positive Response Service ID 
n 
XX 
Byte n (where n <= 255) 
Negative Response: 
Response 
Byte 
Value 
Byte Description 
1 
7F 
Negative Response Service ID 
2 
XX 
Request Service ID 
3 
XX 
Response Code 
 
Pseudo Code: 
XX OP AC0 AC1 AC2 AC3 G0-G1 G2-G3 G4-G5 G6-G7 G8-G9 
Get response for the request 
If a timeout occurred 
Goto No Communication Processing 
Endif 
If a negative response service ID is returned (negative response service ID $7F) 
If the negative response code = expected positive response service ID plus $40) 
Set 7f-special process flag 
**(see details below) 
Endif 
Return negative response 
Else 
Return positive response 
Endif 
** Special Case 7F processing
:
 
If the service request
has a negative response code that 
is the same as
an
expected positive response 
message response service ID plus $40: 
The 7f-special-process flag will be set. The Interpreter shall look for the