CP3BT23_14 Datasheet, PDF (131/324 Pages) Texas Instruments – CP3BT23 Reprogrammable Connectivity Processor with Bluetooth and Dual CAN Interfaces

CP3BT23
www.ti.com
SNOSCX3A – JULY 2013 – REVISED JANUARY 2014
Error States
The device can be in one of five states with respect to error handling (see Figure 18-10).
External Reset or
Enable CR16CAN
SYNC
11 consecutive 'recessive" bits
received
ERROR
ACTIVE
(TEC OR REC) > 95
(TEC AND REC) < 96
ERROR
WARNING
128 occurrences of
11 consecutive 'recessive" bits
(TEC OR REC) > 127
(TEC AND REC) < 128
ERROR
PASSIVE
TEC > 255
BUS
OFF
Figure 18-10. Bus States
DS027
Synchronize
Once the CAN module is enabled, it waits for 11 consecutive recessive bits to synchronize with the bus.
After that, the CAN module becomes error active and can participate in the bus communication. This state
must also be entered after waking-up the device using the Multi-Input Wake-Up feature. See
Section 18.11.
Error Active
An error active unit can participate in bus communication and may send an active (“dominant”) error flag.
Error Warning
The Error Warning state is a sub-state of Error Active to indicate a heavily disturbed bus. The CAN
module behaves as in Error Active mode. The device is reset into the Error Active mode if the value of
both counters is less than 96.
Error Passive
An error passive unit can participate in bus communication. However, if the unit detects an error it is not
allowed to send an active error flag. The unit sends only a passive (“recessive”) error flag. A device is
error passive when the transmit error counter or the receive error counter is greater than 127. A device
becoming error passive will send an active error flag. An error passive device becomes error active again
when both transmit and receive error counter are less than 128.
Bus Off
A unit that is bus off has the output drivers disabled, i.e., it does not participate in any bus activity. A
device is bus off when the transmit error counter is greater than 255. A bus off device will become error
active again after monitoring 128 × 11 “recessive” bits (including bus idle) on the bus. When the device
goes from “bus off“ to “error active“, both error counters will have a value of 0.
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CAN Module 131