CAN Notes (10) the type of error and the output
1. Error species
There are five kinds of errors, many errors may also occur:
- Bit error
- Stuff Error
- CRC error
- wrong format
- ACK error
Kind of error, contents of error, frame error detection means detecting and Table:
| The wrong kind | Wrong content | Erroneous detection frame (segment) | Detecting means |
|---|---|---|---|
| Bit error | Level comparison output level bus (excluding padding bits), when the two are not the same power level of the detected error | Data frame (SOF~EOF) | A transmitting unit, a receiving unit |
| Data frame (SOF~EOF) | |||
| Error Frame | |||
| Overload Frame | |||
| Stuff Error | Bit stuffing in the required period, the same error is detected continuously electrically 6 usually detected | Data frame (SOF~CRC order) | A transmitting unit, a receiving unit |
| Remote frame (SOF~CRC order) | |||
| CRC error | Calculated from the received data CRC to the received CRC result is not the same as the order of the detected error | Data frames (CRC sequence) | The receiving unit |
| Remote frame (CRC sequence) | |||
| wrong format | When an error is detected format segment opposite the fixed bit format detected | Data frame (CRC delimiter, ACK delimiter, EOF) | The receiving unit |
| Remote frame (CRC delimiter, ACK delimiter, EOF) | |||
| Error delimiter | |||
| Overload delimiter | |||
| ACK error | Transmission means detects an error in the ACK slot recessive level detected (when the detected error is not transmitted from ACK) | A data frame (ACK channel) | Transmission unit |
| Remote frame (ACK channel) |
1.1. Bit error
-
To output data on the bus frame, remote frame, the error frame, the frame unit by the overload
detecting means and the output of the ACK, an error output unit -
In the output recessive level arbitration period, but detected a dominant level
will not be regarded as bit errors, but lost in arbitration -
Output recessive bit in the arbitration field as the filling level, the dominant level is detected but
the error bit is not considered, but mistakes filling -
Transmitting unit outputs an ACK segment in a recessive level, the dominant level is detected but
the error bit is not considered, but other units are determined as ACK response -
Passive output error flag (6 recessive bits) but dominant level is detected, an error flag will comply with the conditions of the end
wait detected six bit value (explicit or implicit) consecutive identical bits is not considered error
1.2. Malformed
-
Even if the receiving unit detects EOF (7 bits recessive bits) of the last (first 8 bits) to a dominant level
is not considered malformed -
Even if the receiving unit detects a data length code value (DLC) in the 9~15
not considered malformed
2. The output of error frames
Flag error detection means outputs a communications error satisfies an error condition
The error flag in the active cell output error state is an active error flag six dominant bits 0
error flag output unit in an error passive state passive error flag 6 recessive bits 1
After completion of the transmission unit transmits an error frame, transmitting data frames or remote frames again
Error flag output timing such as:
| The wrong kind | Output Timing |
|---|---|
| Bit error | From an error is detected after the start of an error flag output |
| Stuff Error | |
| wrong format | |
| ACK error | |
| CRC error | Under ACK after a start delimiter error flag output |
Reference:
"CAN Primer"
Related Recommended:
CAN Notes (9) bit stuffing
CAN Notes (8) priority
CAN Notes (. 7) CAN protocol (ii)
CAN Notes (. 6) CAN protocol (a)
CAN Notes (5) standard protocol
Thank you!