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
Error control
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.
Counting up the error counter and the status transition conditions
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. |
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| HALT: Sending and receiving disabled. |
BUSOFF: Sending and receiving disabled. |
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| 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.
