ADSP-BF537 Blackfin Processor Hardware Reference
9-29
CAN Module
•
Acknowledge error
An acknowledge error occurs whenever a message has been sent and
no receivers drive an acknowledge bit.
•
CRC error
A CRC error occurs whenever a receiver calculates the CRC on the
data it received and finds it different than the CRC that was trans-
mitted on the bus itself.
•
Stuff error
The CAN specification requires the transmitter to insert an extra
stuff bit of opposite value after 5 bits have been transmitted with
the same value. The receiver disregards the value of these stuff bits.
However, it takes advantage of the signal edge to resynchronize
itself. A stuff error occurs on receiving nodes whenever the 6th
consecutive bit value is the same as the previous five bits.
Once the CAN module detects any of the above errors, it updates the
error status register
CAN_ESR
as well as the error counter register
CAN_CEC
.
In addition to the standard errors, the
CAN_ESR
register features a flag that
signals when the
CANRX
pin sticks at dominant level, indicating that
shorted wires are likely.
Error Frames
It is of central importance that all nodes on the CAN bus ignore data
frames that one single node failed to receive. To accomplish this, every
node sends an error frame as soon as it has detected an error. See
Once a device has detected an error, it still completes the ongoing bit and
initiates an error frame by sending six dominant and eight recessive bits to
the bus. This is a violation to the bit stuffing rule and informs all nodes
that the ongoing frame needs to be discarded.
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...