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FlexRay - Error control | Cypress Semiconductor

FlexRay - Error control

 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


FlexRay has three error processing levels.

FlexRay's errors and processing levels

Item Normal active Normal passive Fault
Status Complete operation Reduced operation Stop operation
Frame processing Frame sending and receiving enabled Frame sending stopped
Frame receiving enabled
Frame sending and receiving stopped
Clock synchronization Synchronized Maintain synchronization Out of synchronization
Action Fully maintained synchronization When the received frame is processed and it is clock-synchronized, it recovers to normal active state autonomously. For restarting operation, reset or instruct to transit to the Ready state from the host.

The error status transition is managed with the error counter.
The error counter values including a clock synchronization error and clock correction value error depends on application, so it is determined at system designing.

Error status transition

In the management of error counter, it controls the clock synchronous error monitoring operations using the error counters for error status detection and for recovery from the error state separately.

Clock synchronization error monitoring operation (error detection)

  • The clock synchronization error detection is judged with the number of continuous failures of the clock synchronization processing (rate correction and offset correction).
  • The fault/normal passive transition requirements can be specified from the host.
  • Whether or not to perform error transition can be specified from the host.

Error status transition

Clock synchronization error monitoring operation (normality detection)

  • The clock synchronization normality detection is judged with the number of continuous normal clock corrections (rate correction and offset correction).
  • The normal active return transition requirement can be specified from the host.
  • By specifying 0 to this return transition requirement, it can refuse to return to normal active state

Counting down the error counter and the status transition conditions

Comparison of error processing of FlexRay and CAN

Item FlexRay CAN Remarks
Error state NORMAL_ACTIVE:

Normal operation
ERROR_ACTIVE:

Normal operation
CAN monitors the bus status when it becomes "bus off," and if it detects idle time for a certain time, it decodes it.



FlexRay requires reset processing by CPU when a halt occurs.
NORMAL_PASSIVE:

Sending disabled, receiving enabled.
ERROR_PASSIVE:

Sending and receiving enabled, error frame sending disabled.
HALT:

Sending and receiving disabled.
BUSOFF:

Sending and receiving disabled.
Status transition management Management with error counter

The counter value in the status transition condition is determined at system designing.

It controls using the error counters for error status detection and for recovery from the error state separately.
Management with error counter

The counter value in the status transition condition is a fixed value.

It has the error counters for sending and receiving separately, and each of them counts up and down according to normal or error transition detections.
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Error affecting the error counter management Clock synchronization error only

Rate correction and offset correction failed.
Bit error

Staff error

CRC error

Form error

ACK error
FlexRay set an error flag unless a clock synchronization error occurs, and it generates an interrupt.
Error report to the bus Not reported Reported

It sends an error frame.
FlexRay performs managements such as network management.

- Note -

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