Functional Operation
9-28
ADSP-BF537 Blackfin Processor Hardware Reference
CAN Warnings and Errors
CAN warnings and errors are controlled using the
CAN_CEC
register, the
CAN_ESR
register, and the
CAN_EWR
register.
Programmable Warning Limits
It is possible to program the warning level for
EWTIS
(error warning trans-
mit interrupt status) and
EWRIS
(error warning receive interrupt status)
separately by writing to the error warning level error count fields for
receive (
EWLREC
) and transmit (
EWLTEC
) in the CAN error counter warning
level (
CAN_EWR
) register. After powerup reset, the
CAN_EWR
register is set to
the default warning level of 96 for both error counters. After software
reset, the content of this register remains unchanged.
CAN Error Handling
Error management is an integral part of the CAN standard. Five different
kinds of bus errors may occur during transmissions:
•
Bit error
A bit error can be detected by the transmitting node only. When-
ever a node is transmitting, it continuously monitors its receive pin
(
CANRX
) and compares the received data with the transmitted data.
During the arbitration phase, the node simply postpones the trans-
mission if the received and transmitted data do not match.
However, after the arbitration phase (that is, once the
RTR
bit has
been sent successfully), a bit error is signaled any time the value on
CANRX
does not equal what is being transmitted on
CANTX
.
•
Form error
A form error occurs any time a fixed-form bit position in the CAN
frame contains one or more illegal bits, that is, when a dominant
bit is detected at a delimiter or end-of-frame bit position.
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 ...