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Class 2 Response Processing
Supported By:
Class 2 Interpreter 1
Description:
The Response Processing defines how the tool deciphers the response(s) returned
from a control module
after a successful request has been transmitted to the control module **.
The response buffer fields, filled when a controller responds to a message, are identified as follows:
Byte 1
- Priority and
Message Type
Byte 2
- Target Address
(typically targeted to the tester device)
Byte 3
- Source Address (typically sent from a control module)
Byte 4
- Message ID
(typically a positive/negative response ID)
Byte 5
- Misc. Response Data (N = 4096 bytes max.)
Byte N+5 - High Byte of Block Transfer
Message Checksum
Byte N+6 - Low Byte of Block Transfer Message Checksum
**
Note
:
-
There are some Class 2 Op-Codes that send out a request and do not look for a response (i.e. Ignore
Response).
-
There are some Class 2 Op-
Codes that send out a request and don‟t care if there are no responses
(i.e. Ignore Error).
-
There are some Class 2 Op-
Codes that do not support the “no comm.” („FD‟) processing.
These special cases are defined within the individual Class 2 Op-Codes.
Pseudo Code:
“Ignore Response” Processing
If the op-
code specifies a response processing type of “Ignore Response”
No response messages will be processed (read) from the vehicle communication link.
Response
processing will return immediately with “Success” after the request
has been transmitted
Endif
“Ignore Error” Processing
If the op-
code specifies a response processing type of “Ignore Error”
The response data (one or more messages) WILL be processed (read) from the vehicle communication
link (based on “FE Response Processing” or “Individual Device Response Processing”).
Regardless of whether the response is a positive, negative, or
no response is received,
response
processing will return with “Success”
Endif
“FE” (all devices)
Response Processing
If the request message is targeted to “all” (FE) devices
Process the response from the controller(s) on the
vehicle communication link
(only for controllers that respond to the “FE” request)
If a negative (
7F) response is processed from one of the “responding” controllers
Return immediately with “failed” (negative response) and the data from the negative response
Endif
Wait for 2 seconds of no responses being processed (idle vehicle communication link)
If after 2 seconds there have been NO responses processed (zero in total)
Return with a “no communication” response
Else
Return with “Success” and the data from the last response processed
Endif
Endif
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“Individual Device” Response Processing
(continued)
If the request message is targeted to a “specific“ device (ex. $10, $11, $18, $28, $40, …)
Process the response from the controller on the vehicle communication link
If a positive response was received (Response Message ID = Mode Number + $40)
Return with “Success” and the positive response data
Endif
If a negative response was received (Response Message ID = 0x7F)
If the last byte of the response is a $23 (Routine Not Complete)
Wait up to one more second for an additional (positive/negative) response
If no more responses are received (in the 1 second)
Return with “failed” (negative response) and the data from the (0x7F . . . 0x23) response
Endif
Endif
If the Response Message “target address” does not equal the Request Message “source address”
Keep attempting to process responses from the controller
If no more responses are received (in the remaining amount of time)
Return with “failed” (negative response) and the data from the mis-matched target/source
response
Endif
Endif
Endif
If “no response” was ever received from the individual device
Return with a “No Communication” response
Endif
Special Mode $36 Response Processing
If a positive response was received (Response Message ID = $76)
If “response code” data byte is a $78 or a $6F (Response Data Byte #2 – “action not yet complete”)
Keep attempting to process responses from the controller until a “true” positive
or negative is
received
Endif
Endif
Endif
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