[51] CAN protocol Queries

Hi All,

what are the types of 32 message objects
(or)
list out 32 message object
what is use of function code its types(4 bits) and identifier types(7 bits) in Basic CAN
how many message objects and its types

first priority for identifier or for Message objects.

what happens a node transmit a broadcast message or data, some devices or nodes received data correctly and some devices received error then what happens

how to give priority, message base or identifier base

what is the use of Non return zero in Bit stuffing or stuff error.

Thanks & Regards,
Subbi Reddy.

what is the use of Non return zero in Bit stuffing or stuff error.

Answer - > bit stuffing is done in CAN for synchronisation & to avoid errors , in CAN protocol synchronisation happens with the help of edge hence after 5 consecutive homogeneous bits edge is inserted to ensures synchronization of all nodes. When five consecutive bits of the same level have been transmitted by a node, it will add a sixth bit of the opposite level to the outgoing bit stream. The receivers will remove this extra bit. when CAN node fails to do this stuff error occures i.e if more than five consecutive bits of the same level occurs on the bus, a Stuff Error is signaled.

what happens a node transmit a broadcast message or data, some devices or nodes received data correctly and some devices received error then what happens

hi
every CAN controller has machanism to detect errors, if error is found by one of CAN controller it will transmit error flag, this will inturrupt bus traffic.other can controllers will also detect this error caused by error flag after that they will discard that massage.
every can node has two error counters transmit and receive error counter. CAN node who detects error will increase transmit error counter while other node will increase receive error counter.

then according to number of counts in error count we have active, passive and bus off state.
like till this count is 127 CAN node is in active state , between 127 - 255 in passive state and above that went into busoff state. CAN node with passive state has lower priority to transmite while node with bus off state is disconnected from communication and does not allowed to take participation in activities.