ST72521M/R/AR
CONTROLLER AREA NETWORK (Cont’d)
– ERROR. The error management as described in
the CAN protocol is completely handled by hard-
ware using 2 error counters which get increment-
ed or decremented according to the error
condition. Both of them may be read by the appli-
Figure 70. CAN Error State Diagram
cation to determine the stability of the network.
Moreover, as one of the node status bits (EPSV
or BOFF of the CSR register) changes, an inter-
rupt is generated if the SCIE bit is set in the ICR
Register. Refer to Figure 70.
When TECR or RECR > 127, the EPSV bit gets set
ERROR ACTIVE
ERROR PASSIVE
When 128 * 11 recessive bits occur:
- the BOFF bit gets cleared
- the TECR register gets cleared
- the RECR register gets cleared
When TECR and RECR < 128,
the EPSV bit gets cleared
When TECR > 255 the BOFF bit gets set
and the EPSV bit gets cleared
BUS OFF
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