WhatIsWrongWithRTR

Why using RTRs is not advised?

CiA, especially the Special Interest Group CANopen is not recommending using RTR Messages. You may ask: why?

The CiA has a paper explaining the contras and giving advice for better solutions. CiA AN 802 V1.0: CANopen statement on the use of RTR-messages

It can be downloaded free of charge after a registration at http://www.can-cia.org/downloads/ciaspecifications/?1324 .

In short the main topics:

• The number of transmit messages buffers supporting CAN remote frames is limited on most so-called FullCAN controllers.
• Implementation of a CAN driver handling RTR is much more complex. On some controllers impossible.
• Some CAN controllers react different on the 'data length' code in the RTR frame and the data frame. This is due to differences in the CAN implementation.