Analog Devices ADSP-SC58 Series Hardware Reference Manual page 1228

Receive Operation
Figure 25-10: CAN Receive Operation Flowchart
Data Acceptance Filtering
If Device Net mode is enabled (CAN_CTL.DNM = 1) and the mailbox is set up for filtering on data field, the filter-
ing occurs on the standard ID of the message and data fields. The data field filtering can be programmed for either
the first byte only or the first 2 bytes, as shown the Data Field Filtering table.
If the CAN_AM[nn]H.FDF bit is set, the corresponding
bits 15:0]). If the CAN_AM[nn]H.FDF bit is cleared, the corresponding
tended identifier mask (CAN_AM[nn]H.EXTID bits 15:0).
Table 25-4: Data Field Filtering
FDF (Filter on Data Field)
0
0
1
1
Watchdog Mode
Watchdog mode ensures that messages are received periodically. It also observes whether a certain node on the net-
work is alive and functioning properly. Watchdog mode detects and manages the failure cases, as needed.
Enable this mode by programming the universal counter to watchdog mode by setting the CAN_UCCNF.UCCNF
to 0x2. Once enabled, the
counter decrements at the CAN bit rate.
25–12
FROM MESSAGE RECEIVER/PREVIOUS MAILBOX
COMPARE ALL
BITS
RECEIVE
MAILBOX
READY?
SAVE MESSAGE
TO MAILBOX
EXIT
FMD (Full Mask Data Field)
0
1
0
1
register is loaded with the predefined value contained in CAN_UCRC. This
CAN_UCCNT
ADSP-SC58x/ADSP-2158x SHARC+ Processor Hardware Reference
N
MAILBOX
ENABLED?
Y
COMPARE
1
0
AME? UNMASKED
BITS ONLY
N
MATCH?
Y
TRANSMIT
MAILBOX
DIRECTION?
N
REMOTE
MAILBOX?
Y Y
Y
OVERWRITE
PROTECTION?
N
REPORT TRANSMIT
OVERFLOW REMOTE
ERROR MESSAGE
EXIT EXIT
CAN_AM[nn]L
CAN_AM[nn]L
Description
Do not allow filtering on the data field
Not allowed. FMF must be 0 when FDF is 0
Filter on first data byte only
Filter on first two data bytes
NEXT MAILBOX
NEXT MAILBOX
N
NEXT MAILBOX
NEXT MAILBOX
register holds the data field mask (DFM
register holds the ex-