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7682C–AUTO–04/08
AT90CAN32/64/128
19.11 MOb Registers
The MOb registers has no initial (default) value after RESET.
19.11.1
CAN MOb Status Register - CANSTMOB
Bit 7 – DLCW: Data Length Code Warning
The incoming message does not have the DLC expected. Whatever the frame type, the DLC
field of the CANCDMOB register is updated by the received DLC.
Bit 6 – TXOK: Transmit OK
This flag can generate an interrupt. It must be cleared using a read-modify-write software routine
on the whole CANSTMOB register.
The communication enabled by transmission is completed. TxOK rises at the end of EOF field.
When the controller is ready to send a frame, if two or more message objects are enabled as
producers, the lower MOb index (0 to 14) is supplied first.
Bit 5 – RXOK: Receive OK
This flag can generate an interrupt. It must be cleared using a read-modify-write software routine
on the whole CANSTMOB register.
The communication enabled by reception is completed. RxOK rises at the end of the 6th bit of
EOF field. In case of two or more message object reception hits, the lower MOb index (0 to 14)
is updated first.
Bit 4 – BERR: Bit Error (Only in Transmission)
This flag can generate an interrupt. It must be cleared using a read-modify-write software routine
on the whole CANSTMOB register.
The bit value monitored is different from the bit value sent.
Exceptions: the monitored recessive bit sent as a dominant bit during the arbitration field and the
acknowledge slot detecting a dominant bit during the sending of an error frame.
Bit 3 – SERR: Stuff Error
This flag can generate an interrupt. It must be cleared using a read-modify-write software routine
on the whole CANSTMOB register.
Detection of more than five consecutive bits with the same polarity. This flag can generate an
interrupt.
Bit 2 – CERR: CRC Error
This flag can generate an interrupt. It must be cleared using a read-modify-write software routine
on the whole CANSTMOB register.
The receiver performs a CRC check on every de-stuffed received message from the start of
frame up to the data field. If this checking does not match with the de-stuffed CRC field, a CRC
error is set.
Bit
7
6
5
4
3
2
1
0
DLCW
TXOK
RXOK
BERR
SERR
CERR
FERR
AERR
CANSTMOB
Read/Write
R/W
Initial Value
-