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FlexRay - Electronic signals | Cypress Semiconductor

FlexRay - Electronic signals

 Background |  Overview |  Features |  In-car Communication Protocol |  Target applications |  Data transfer method |  Difference with CAN |  Internal configuration of a node |  Electronic signals |  Bus Guardian |  Topology |  Segment configuration |  Protocol |  Status transition |  Error control |

FlexRay ASSP

Four bus statuses, Idle_LP, Idle, Data_1, and Data_0 are defined.

The bus communicates by using the differential signals, BP and BM. The voltage on each differential signal is represented by uBP or uBM.

The electronic signals of FlexRay are shown below.

 Electronic signals of FlexRay

  • Idle_LP status means low-power status.
  • Idle_LP status means idle (no-communication) status.
  • Data_1 status means logical HIGH.
  • Data_0 status means logical LOW.

    (The conflict of Data_1 and Data_0 is not allowed.)

The following shows the monitored actual FlexRay communication signals.

The red waveform data indicates BP signal, and the green one represents BM signal.

 Normal access signals

100MS/s 500ns/div

 Signals change from Idle_LP to Idle, and to start of communication.

10MS/s 100ms/div

The voltage drop on the circuit harness, connector, and common mode choke, margin of induced drop, and the incompatibility occurred at the pin need to be considered in terms of signal integrity.

FlexRay provides minimum requirements that a test plane must be carried out on both the sending and receiving sides in the network.

  • Test plane 1: Bus driver BP and BM pins of the sending node
  • Test plane 2: BP and BM connector pin on the network input side
  • Test plane 3: BP and BM connector pin on the network output side
  • Test plane 4: Bus driver BP and BM pins of the receiving node

A signal eye-diagram for each test plane is defined to indicate the minimum aperture of the test plane differential voltage.

The voltage is in [mV] unit, and the time is the gdBit percentage.

 FlexRay test plane and signal eye-diagram (TP1, TP4)

- Note -

Some parts of this site show only the outlines of the actual FlexRay standards to make them easily understood.