CAN is a request-response bus, you send a query, get ACK, then queried chip sends response. If you need to read something, you query for it. You can do queries

CAN is a request-response bus, you send a query, get ACK, then queried chip sends response. If you need to read something, you query for it. You can do queries like "start giving me rpm data every 1s", but you need to query for this, also ecu has limited resources for such queries, so you need to switch between different sets of data. Of course if something else requests such data you can listen for it too.