Reliable Diagnostics of a MOST System

March 06, 2014 // By Dr. Terezia Toth
A MOST infotainment network has high demands regarding performance and stability. Developers are aware that in case of a critical failure a powerful method for analyzing the network is needed. Ruetz System Solutions, as part of the MOST Compliance Technical Group (MCTG), has developed an efficient test system for the Electrical Control Line.

Network Failure Diagnostics

If failures are not found and not solved quickly, the car is held up at the car workshop and that means consumer loss of trust in the quality of the car as a product. To avoid this loss and fulfill important diagnostic purposes, the MOST Cooperation has introduced the Electrical Control Line (ECL) as a new optional feature for MOST150. ECL is the key element to increase diagnostic capability in a MOST system. It is the way to detect and allocate errors in the MOST system via an additional wire line. This wire line can also be used to generate an electrical wake-up signal.

The ECL protocol provides a variety of functionalities which can be divided into two separate groups:

  • Triggering a system test and
  • Waking up the system by an electrical wake-up signal.

A device connected to the ECL can act in the role of an initiator and/or in the role of a participant. Because of the two separate functions there are two roles for each:

  • System test initiator triggers the test and collects the test results,
  • System test participant report the test results.
  • Electrical wake-up initiator creates the electrical wake-up signal,
  • Electrical wake-up participant is woken up by this signal.

There is exactly one system test initiator, but eventually more than one electrical wake-up initiator in a MOST system.

A system test message has three sequences: start sequence, parameter sequence and result sequence. Each message is initiated by the initiator and starts with system test start impulse and optional retries, followed by the parameter sequence. The initiator generates five parameter values, which together define one of the four kinds of system test:

  • Ring break diagnosis (00000)
  • Alive (10000)
  • Coding error / threshold (01000)
  • Sudden signal off / critical unlock (11000)

Electrical Control Line in a MOST Network

ECL is limited to MOST systems with a maximum of 20 devices. Each device gets a unique node

Design category: