MOST150 test solution supports coax PHY

April 20, 2016 // By Christoph Hammerschmidt
As an extension to its existing Physical Layer Stress Test tool for the MOST150 infotainment data bus Ruetz System Solutions introduced a module dedicated to perform such tests in a coax cable environment. The add-on has become necessary because MOST150 recently offers support for this type of cables.

The new MOST Tester Cable Module (MTCM) meets the additional requirements related to coax versions, the Munich (Germany) based company said in a press release. The MTCM is a highly integrated solution to implement the limited MOST150 cPHY test setup for MOST150 that fulfills all requirements of the MOST150 cPHY Compliance Verification Procedure, said Ruetz CEO Wolfgang Malek. It facilitates the migration from a MOST150 oPHY test setup to a MOST150cPHY test setup if the Physical Layer Stress Test tool (PhLSTT) is used. The cPHY is based on 50-Ohm cabling and supports simplex as well as duplex transmission. The central functionality of the MTCM is emulating a transfer function that represents typical in-car coax interconnections. The PhLSTT creates the MOST150 pattern that feeds the device under test (DUT). An internal microcontroller controls all functions of the MOST Tester Cable accessed by a serial interface. A documented application-programming interface is available. Thus, Ruetz provides an automated solution t incorporating the complete MOST150 limited cPHY test setup. It consists of the PhLSTT, the MOST Tester Cable Model, a power supply, and an optional temperature chamber.


The test system defines three different cable models in order to simulate a transmission channel, thus covering typical use cases in the car. A transmitter with adjustable rise and fall times drives these cable models, which represent a short, mid and long transmission line. For duplex operation, an integrated coupler separates the incoming signal from the outgoing. Thereby, this signal can be used for oscilloscope measurements and a return path to the PhLSTT. In terms of measuring MOST signals, the cPHY technology offers the advantage of the transmission system to be terminated by 50 Ohms and therefore an oscilloscope can directly connect to it without an additional probe. The MCTM provides a test solution for simplex as well as for duplex operations. For duplex operations, an additional noise input is available to connect an external signal