RS485 Meets CAN

The new TTP/A (Time Triggered Protocol type A) field bus technology embraces both RS485 and CAN and is now being introduced into automotive and process control applications.The TTP/A protocol allows a CAN bus device and an RS485 transceiver to work together in the same system. Originally, the CAN bus was designed for use in automotive applications, while the RS485 bus was designed for process control applications. In this article we will show how to operate the two systems on a single bus at data rates up to 1 Mbit/s.CAN and RS485 use a practically identical data transfer medium: both systems send data differentially over twisted-pair cable. The signal levels, however, are different, and so communication errors will occur of the two systems are connected directly.