32186 datasheet(727/1032 Pages) RENESAS

727 / 1032 page

CAN MODULE

13-117

32185/32186 Group Hardware Manual

Rev.1.10 REJ09B0235-0110 May 15, 07

13.3.3 CAN Controller Error States

The CAN controller assumes one of the following three error states depending on the transmit error and re-

ceive error counter values.

(1) Error active state

• This is a state where almost no errors have occurred.

• When an error is detected, an active error flag is transmitted.

• The CAN controller is in the state immediately after being initialized.

(2) Error passive state

• This is a state where many errors have occurred.

• When an error is detected, a passive error flag is transmitted.

(3) Bus off state

• This is a state where a very large number of errors have occurred.

• CAN communication with other nodes cannot be performed until the CAN module returns to an error active state.

Error Status of the Unit

Transmit Error Counter

Receive Error Counter

Error active state

0–127

AND

0–127

Error passive state

128–255

128 and over

Bus off state

256 and over

–

Transmit error counter > 255

Transmit error counter > 128

Receive error counter > 128

Transmit error counter < 128

AND

Receive error counter < 128

11 consecutive recessive bits

detected on CAN bus 128 times (Note 1)

Error active

state

Error passive

state

Bus off state

Initial setting

Note 1: With RBO (Return Bus Off) bit and FRST (Forcible Reset) bit, it can be forcibly exited from

bus off state. For detail, see CAN Control Register (CANnCNT).

13.3 CAN Protocol

Figure 13.3.4 CAN Controller Error States

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