AT7908E
RxClr1: active high, this bit is set to clear the RXOK1 and RXOVR1 bits on the status
register of the receiver message buffers. This bit must be set after the read out opera-
tion of the received message otherwise, at the next reception on the same RX message
buffer, an overrun condition is raised.
Status Registers
STATUS_0
BusOff: this bit indicates that the CAN controller has reached a bus off condition.
ErrPass: this bit indicates that the CAN controller has reached an error passive
condition.
TxActive: this bit signals that there is an active transmission.
TxOK: this bit indicates that the transmission has been successfully terminated. This bit
is reset automatically when the TXREQ bit on the SETUP_3 register is set.
Rxbuf1:Rxbuf0: these bits indicate which receiver buffer received a message:
00 : message filtered out
01 : message received by RX1 buffer
10 : message received by RX2 buffer
11 : message received by RX3 buffer
SyncRx: this bit indicates that a pulse on the sync bit of the received message has been
generated.
SyncTx: this bit indicates that a pulse on the sync bit of the transmitted message has
been generated.
STATUS_RX:
RXOVR3: This bit indicates an overrun condition (a new message received on the mes-
sage buffer 3 with RXOK3 not cleared).
RXOVR2: This bit indicates an overrun condition (a new message received on the mes-
sage buffer 2 with RXOK2 not cleared).
RXOVR1: This bit indicates an overrun condition (a new message received on the mes-
sage buffer 1 with RXOK1 not cleared).
RXOK3: This bit indicates (active high) that the data frame message has been received
correctly by the third message buffer.
RXOK2: This bit indicates (active high) that the data frame message has been received
correctly by the second message buffer.
RXOK1: This bit indicates (active high) that the data frame message has been received
correctly by the first message buffer.
Filter Registers
The 2 filter registers are used (together with the arbitration register of the receiver buf-
fers or the arbitration registers of the transmit buffer to answer to the remote request) to
filter out the messages that are not interesting for the receiving software. The filtering
function is implemented only on 11 bits of the identifier (message_id28 downto
message_id18) but works for both, extended and standard messages. The filtering func-
tion is:
Message Valid if:
for i = 28 downto 18
(“MsgID(i)” XOR “RXnARB(i)” )AND “AM(i)” = 0
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4268D–AERO–11/09
ATMEL [ ATMEL ]
