DS80C390 datasheet(85/155 Pages) DALLAS

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DS80C390 High-Speed Microcontroller User’s Guide Supplement

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ER2-0

Bit 2-0

CAN 1 Bus Error Status. These bits indicate the type of error, if any, detected

in the last CAN 1 Bus Frame. These bits will be reset to the 111b state following

any read of the C1S register (when SWINT=0), allowing software to determine if

a new error has been received since the last read of this register. The ER2-0 bits

are read only.

The ER2-0 bits are updated any time they change from 000b or 111b to another

value. If enabled, an interrupt will be generated at this time. Errors received while

the ER2-0 bits are in a non-000b or 111b state will be ignored, leaving ER2-0

unchanged and not generating enabled interrupts. This ensures that error

conditions will not be lost/overwritten before software has a chance to read the

C1S register. Once the C1S register is read and the ER2-0 bits return to 111b, new

errors will be processed normally. In the case of simultaneous errors in multiple

CAN 1 message centers, only the highest priority error is indicated.

ER2

ER1

ER0

Priority

Error Conditions

N/A

No Error in Last Frame

Bit Stuff Error

Format Error

Transmit Not Acknowledged Error

6(lowest)

Bit 1 Error

1(highest)

Bit 0 Error

CRC Error

N/A

No change since last C1S read

The following is a description of the different error types:

Bit Stuff Error

: Occurs when the CAN controller detects more than 5 consecutive

bits of an identical state are received in an incoming message.

Format Error

: Generated when a received message has the wrong format.

Transmit Not Acknowledged Error

: Indicates that a data request message was sent

and the requested node did not acknowledged the message.

Bit 1 Error

: Indicates that the CAN attempted to transmit a message and that

when a recessive bit was transmitted, the CAN bus was found to have a

dominant bit level. This error is not generated when the bit is a part of the

arbitration field (identifier and remote retransmission request).

Bit 0 Error

: Indicates that the CAN attempted to transmit a message and that

when a dominant bit was transmitted, the CAN bus was found to have a

recessive bit level. This error is not generated when the bit is a part of the

arbitration field. The Bit 0 Error is set each time a recessive bit is received

during the Busoff recovery period.

CRC Error

: Generated whenever the calculated CRC of a received message does

not match the CRC embedded in the message.

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