### Error­frames : which node sent the messa­ge

When error­frames occur in a bus, 2 ques­ti­ons come up :

1. Which node des­troy­ed the messa­ge by sen­ding an error­frame ?
2. Which node sent the messa­ge that was later des­troy­ed ?

The first ques­ti­on is not easy to ans­wer, becau­se every node in a bus can be the sen­der of the error­frame, it will look ali­ke every time. This pro­blem can only be found by mea­su­ring on dif­fe­rent pla­ces in the bus and tem­por­ar­ly dis­con­nect one node after the other.

To ans­wer the second ques­ti­on, we have a fair chan­ce to ans­wer it with the CBT2.
By using the online trig­ger mea­su­rement you are able to show the last fla­wed messa­ge wit­hin the oscil­lo­scope dis­play. The­re­fo­re you should trig­ger to error­frames only (dis­mark the other trig­gers on the left side).

Now start a sin­gle mea­su­rement, the tes­ter stops at the next error­frame. Da last messa­ge is now dis­play­ed in the oscil­lo­scop dis­play. You have a good chan­ce that the error­frame came after the arbi­tra­ti­on, so you can read the ID of the node that sent the messa­ge. In the screen­shot it is ID 702 (the green mar­ked area of the oscil­lo­gram is the ID).