Testing the MOST150 Coax Physical Layer

June 09, 2016 // By Jörg Angstenberger and Frederic Garraud, Ruetz System Solutions
New challenges and demands for Physical Layer Testing occur with the introduction of an additional Physical Layer for MOST150, based on 50 Ohm coax connections for simplex and duplex transmission.

A sophisticated concept for Physical Layer Testing on ECU level was already created for the MOST150 optical Physical Layer. The test usually establishes a running network and enables access to the transmitter output, thereby verifying the majority of parameters, which were defined at the specification point of the transmitter output, SP2. In addition, a consistency test of received bit information is performed while the receiver input is provided by a stress test pattern via different transmission channels representing the limits of the MOST Physical Layer Specification.

During the last few years, this test concept was successfully used to perform MOST150 limited optical Physical Layer Tests , and therefore, it is a feasible starting point for developing a test setup that covers the demands for the MOST150 cPHY Technology.

Requirements for MOST150 Test Setups

Figure 1 shows the different test setups for simplex and duplex cPHY testing and the oPHY test setup for comparison. A MOST Tester device (Physical Layer Stress Test Tool - PhLSTT) is used to build up an operating ring network, acts as a stress test generator, checks for data consistency, and reads stored failures from the ECU memory of the device under test (DUT). In the test setup for MOST150 limited oPHY, which is described in MOST150 oPHY Compliance Verification Procedure [1], the PhLSTT is able to generate additional stress for the DUT by changing the duty cycle of the MOST150 pattern. Different optical transmission channels are simulated by using a 2m fiber for a high bandwidth channel and a 15m fiber in combination with a mode scrambler for a low bandwidth channel. An integrated optical attenuator enables different input power levels. An optical splitter in the TX path of the DUT provides access to the SP2 interface and also a return path to the PhLSTT.


Figure 1: MOST150 Limited Physical Layer Setups
For higher resolution click here

The test setup for MOST150 limited cPHY, described in

Design category: