STR720 datasheet(214/401 Pages) STMICROELECTRONICS

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STR720 - CONTROLLER AREA NETWORK (CAN)

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Bits 2:0

LEC[2:0]: Last Error Code (Type of the last error to occur on the CAN bus)

The LEC field holds a code, which indicates the type of the last error to

occur on the CAN bus. This field will be cleared to ‘0’ when a message has

been transferred (reception or transmission) without error. The unused code

‘7’ may be written by the CPU to check for updates. Table 49 describes the

error codes.

Table 49. Error Codes

Error Code

Meaning

0No Error

Stuff Error: More than 5 equal bits in a sequence have occurred in a part of a

received message where this is not allowed.

Form Error: A fixed format part of a received frame has the wrong format.

AckError: The message this CAN Core transmitted was not acknowledged by

another node.

Bit1Error: During the transmission of a message (with the exception of the arbitra-

tion field), the device wanted to send a recessive level (bit of logical value ‘1’), but

the monitored bus value was dominant.

Bit0Error: During the transmission of a message (or acknowledge bit, or active

error flag, or overload flag), though the device wanted to send a dominant level

(data or identifier bit logical value ‘0’), but the monitored Bus value was recessive.

During busoff recovery, this status is set each time a sequence of 11 recessive bits

has been monitored. This enables the CPU to monitor the proceedings of the

busoff recovery sequence (indicating the bus is not stuck at dominant or continu-

ously disturbed).

CRCError: The CRC check sum was incorrect in the message received, the CRC

received for an incoming message does not match with the calculated CRC for the

received data.

Unused: When the LEC shows the value ‘7’, no CAN bus event was detected since

the CPU wrote this value to the LEC.

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