Common explanations of active and passive errors in CAN Bus

First, we recommend that you replace the widely used concepts of "active errors" and "passive errors" with "active errors" and "passive errors ".

1. Active error site

Once an error is detected, it immediately sends an error identifier "actively. The so-called "error mark" is itself a "wrong bit sequence" (six consecutive dominant bits, does not meet the "up to five consecutive same-sex bits" requirement of the CAN protocol). The purpose is to "proactively" tell everyone that even if you have not found the "I have discovered" error, now I am making an error! You should see this error!

2. Passive error site

If an error is detected, it can only be "passively" and other people (active site Error Reporting) report an error. When waiting, it can not be connected to the bus, it was not until the "wrong bit sequence" was identified by the active error site: Someone reported an error! Then he can compete for the bus and what should he do.

3. The error identifier has no priority.

4. For a sending site that obtains the right to use the bus through competition, it may listen while sending, and the following situations may occur:

(A) when it finds its own mistakes, it will be flushed and angry (six consecutive same-sex bits ). Just as you practiced writing in kindergarten when you were a child, you will get impatient when you write a wrong stroke, and you will get angry on the paper. The purpose is to tell others (other sites) that an error has occurred!

(B) It does not discover its own errors, but it is found by the receiving site that actively reports errors (for example, errors caused by long lines and high interference ), the site that found the error immediately burst into disorder on the bus (six explicit digits in a row), just as you practiced writing in kindergarten when you were a child, you did not find a wrong stroke, but the teacher (actively reported the site) will be impatient when it finds it, and it will throw on your paper. The purpose is to tell yourself and others (send site and other sites): an error has occurred!

(C) It does not discover its own errors, but as a passive error receiving site, it finds errors (for example, errors caused by long lines and high interference ), this site can only wait slowly for other sites to report errors. If other active error sites do not find the error, wait until the Ack is sent without sending this explicit ack signal to the sending site. Of course, other sites may send this ack, it indicates that no errors have occurred on other sites. No way. Other users can communicate with each other. You cannot! Then you can leave the bus after accumulating a certain amount of data! Wait for a while, get lost, and return to the bus again (at this time, the error records are all cleared, and you must have taken the initiative to report the error site ). As you did when you were a child, you did not find a wrong pen, but it was discovered by other students (passive reporting site, if the instructor wants to beat his ass), he can only wait. When the teacher finds your error (waiting for the initiative to report an error to the site), or the teacher has no eyesight, it will wait until the homework is received, don't accept your (don't send ACK), but the teacher may take the initiative to receive (send ACK to you), then you can't wait, when you become a teacher too (reborn )...

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