25. March 2016 04:41 by Christian
TEC = Transmitter Error Counter
REC = Receiver Error Counter
- When a receiver detects an
error, the REC will be increased by 1, except when the detected error was
a Bit Error during the sending of an Active error Flag or an Overload
- When a receiver detects a
dominant bit as the first bit after sending an Error Flag, the REC will be
increased by 8.
- When a transmitter sends an
Error Flag, the TEC is increased by 8. Exception 1: If the transmitter is
Error Passive and detects an ACK Error because of not detecting a dominant
ACK and does not detect a dominant bit while sending its Passive Error
Flag. Exception 2: If the transmitter sends an Error Flag because a Stuff
Error occurred during arbitration, and should have been recessive, and has
been sent as recessive but monitored as dominant.
- If the transmitter detects a
Bit Error while sending an Active Error Flag or an Overload Frame, the TEC
is increased by 8.
- If a receiver detects a Bit
Error while sending an Active Error Flag or an Overload Flag, the REC is
increased by 8.
- Any node tolerates up to 7
consecutive dominant bits after sending an Active Error Flag, Passive
Error Flag or Overload Flag. After detecting the fourteenth consecutive
dominant bit (in case of an Active Error Flag or an Overload Flag) or
after detecting the eighth consecutive dominant bit following a Passive
Error Flag, and after each sequence of additional eight consecutive
dominant bits, ever y transmitter increases its TEC by 8 and every
receiver increases its REC by 8.
- After successful
transmission of a frame (getting ACK and no error until EOF is finished),
the TEC is decreased by 1 unless it was already 0.
- After the successful
reception of a frame (reception without error up to the ACK Slot and the
successful sending of the ACK bit), the REC is decreased by 1, if it was
between 1 and 127. If the REC was 0, it stays 0, and if it was greater
than 127, then it will be set to a value between 119 and 127.
- A node is Error Passive when
the TEC equals or exceeds 128, or when the REC equals or exceeds 128. An
error condition letting a node become Error Passive causes the node to
send an Active Error Flag.
- A node is Bus Off when the
TEC is greater than or equal to 256.
- An Error Passive node
becomes Error Active again when both the TEC and the REC are less than or
equal to 127.
- A node which is Bus Off is
permitted to become Error Active (no longer Bus Off) with its error
counters both set to 0 after 128 occurrence of 11 consecutive recessive
bits have been monitored on the bus.