Rainbow Electronics T89C51CC02 - Manual (Page 75)

Rev.A - May 17, 2001 75
Preliminary
T89C51CC02
15.6. Fault Confinement
With respect to fault confinement, a unit may be in one of the three following statuses:
•
error active,
•
error passive,
•
bus off.
An error active unit takes part in bus communication and can send an active error frame when the CAN macro
detects an error.
An error passive unit cannot send an active error frame. It takes part in bus communication, but when an error is
detected, a passive error frame is sent. Also, after a transmission, an error passive unit will wait before initiating
further transmission.
A bus off unit is not allowed to have any influence on the bus.
For fault confinement, two error counters (TEC and REC) are implemented.
See CAN Specification for details on Fault confinement.
Figure 61. Line error mode
TEC>255
Error
Active
Error
Passive
Bus
Off
Init.
TEC<127
and
REC<127
TEC>127
or
REC>127
128 occurrences
of
11 consecutive
recessive
bit
TEC: Transmit Error Counter
REC: Receive Error Counter