Process for determining potential shifts between eletronic modules in a wire bus network

A method for determining potential shifts between electronic modules representing bus subscribers, or assigned to said bus subscribers in a wire bus network, or a correspondence quality of communications operating levels of the electronic modules interconnected in the wire bus network, the wire bus network comprising at least one wire bus directly and electrically connected to the electronic modules, the electronic modules being interconnected via a potential busbar serving as a reference-earth potential busbar for bus communications at least during a single-wire operating mode of the wire bus network, the method comprising the acts of:

• (a) determining a bus subscriber to be a test subscriber which is capable, both physically and with regard to potential errors which are possible in a system-specific manner, of communicating with each remaining bus subscriber which may be a potential defective subscriber;
• (b) broadcasting via the test subscriber at least one bus message to put all the bus subscribers to be tested into a “Transmit no application messages” operating mode;
• (c) broadcasting via the test subscriber at least one bus message to put all the bus subscribers to be tested into a RECEIVE ONLY operating mode “receive only, transmission not possible”, as a result of which all the bus subscribers become observational subscribers;
• (d) broadcasting via the test subscriber at least one bus message to put, from amongst a number of observational subscribers, a specific observational subscriber which is a potential defective subscriber into a NORMAL operating mode “transmit and receive”,
• (e) cyclically broadcasting at least one test message by the test subscriber;
• (f) acknowledging the at least one test message via the potential defective subscriber in the NORMAL operating mode by:
• (f) (1) sending a positive acknowledgment back to the test subscriber via the bus using the potential defective subscriber, if the at least one test message is received without any errors by the defective subscriber;
• (f) (2) sending a negative acknowledgment back to the test subscriber via the bus using the potential defective subscriber, if at least one message is received with errors by the defective subscriber;
• and
• (f) (3) sending no acknowledgment onto the bus via the potential defective subscriber, if at least one message is not received by the defective subscriber;
• (g) assessing a positive acknowledgment via the test subscriber as a truth status for data transmission free from errors, and at least one of a negative acknowledgment and the absence of an acknowledgment as a truth status for an erroneous data transmission;
• (h) shifting at least one first source level to which the at least one bus wire used for testing is dominantly keyed using the test subscriber;
• (i) performing acts (f) (1) and (g) to record a range of potential shifting of the at least one source level in which the test message is received without any errors;
• and performing acts (f) (2) and (f) (3) to record a range of potential shifting of the at least one source level in which the test message is one of not received and received with errors;
• (j) setting a potential shift of the source level dominantly assigned to the at least one wire bus to a range in which the test data transmission was previously possible without any errors;
• (k) broadcasting at least one bus message to put the potential defective subscriber into the RECEIVE ONLY operating mode “Receive only—transmission not possible” once the testing of the potential defective subscriber has ended, where the potential defective subscriber becomes the observational subscriber;
• (1) repeating the acts (d) thru (k) for either observational subscribers of specific interest or all observational subscribers;
• (m) evaluating test results;
• and
• (n) returning the wire bus network to a nominal operation using the test subscriber.