RL78/D1A User's Manual: Hardware - Renesas

Under development
Preliminary document
Specifications in this document are tentative and subject to change.
RL78/D1A CHAPTER 14 CAN CONTROLLER
(4) Error state
(a) Types of error states
The following three types of error states are defined by the CAN specification.
- Error active
- Error passive
- Bus-off
These types of error states are classified by the values of the TEC7 to TEC0 bits (transmission error counter
bits) and the REC6 to REC0 bits (reception error counter bits) of the CAN error counter register (C0ERC,
C1ERC) as shown in Table 14-13.
The present error state is indicated by the CAN module information register (C0INFO, C1INFO).
When each error counter value becomes equal to or greater than the error warning level (96), the TECS0 or
RECS0 bit of the C0INFO, C1INFO register is set to 1. In this case, the bus state must be tested because it
is considered that the bus has a serious fault. An error counter value of 128 or more indicates an error
passive state and the TECS1 or RECS1 bit of the C0INFO, C1INFO register is set to 1.
- If the value of the transmission error counter is greater than or equal to 256 (actually, the transmission error
counter does not indicate a value greater than or equal to 256), the bus-off state is reached and the BOFF
bit of the C0INFO, C1INFO register is set to 1.
- If only one node is active on the bus at startup (i.e., a particular case such as when the bus is connected
only to the local station), ACK is not returned even if data is transmitted. Consequently, re-transmission of
the error frame and data is repeated. In the error passive state, however, the transmission error counter is
not incremented and the bus-off state is not reached.
R01UH0317EJ0004 Rev. 0.04 799
Feb. 22, 2013