Can Operation - Analog Devices Blackfin ADSP-BF537 Hardware Reference Manual

The next field of interest is the
sage is an extended frame with a 29-bit identifier instead of an 11-bit
identifier. In an extended frame, the first part of the message resembles
Figure 9-6.
1
SOF IDENTIFIER SRR
Figure 9-6. Extended CAN Frame
As could be concluded with regards to the
field wins arbitration against an extended frame with the same lower
IDE
11-bits, therefore, standard frames are higher priority than extended
frames. The substitute remote request bit (
the reserved bits
( ) are generated automatically by the internal logic.
CRC

CAN Operation

The CAN controller is in configuration mode when coming out of proces-
sor reset or hibernate. It is only when the CAN is in configuration mode
that hardware behavior can be altered. Before initializing the mailboxes
themselves, the CAN bit timing must be set up to work on the CAN bus
that the controller is expected to connect to.
Bit Timing
The CAN controller does not have a dedicated clock. Instead, the CAN
clock is derived from the system clock (
number of time quanta. The Time Quantum (TQ) is derived from the
formula = (
TQ BRP
ADSP-BF537 Blackfin Processor Hardware Reference
IDE
11 1 1 18
IDE IDENTIFIER
and (always sent as dominant), and the checksum
r0 r1
+ )/ , where
1 SCLK BRP
. When set, it indicates that the mes-
1 1 1 4
RTR r1 r0 DLC
field, a dominant bit in the
RTR
, always sent as recessive),
SRR
) based on a configurable
SCLK
is the 10-bit
BRP
CAN Module
field in the
9-9