DS80C390_00 Datasheet, PDF (85/155 Pages) Dallas Semiconductor – High-Speed Microcontroller User’s Guide Supplement

ER2-0
Bit 2-0
DS80C390 High-Speed Microcontroller User’s Guide Supplement
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
0 0 0 N/A
No Error in Last Frame
0 0 12
Bit Stuff Error
0 1 05
Format Error
0 1 14
Transmit Not Acknowledged Error
1 0 0 6(lowest) Bit 1 Error
1 0 1 1(highest) Bit 0 Error
1 1 03
CRC Error
1 1 1 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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