ADSP-BF537 Blackfin Processor Hardware Reference
9-15
CAN Module
Single Shot Transmission
If the single shot transmission feature is used (
OPSSn
=
1
in
CAN_OPSSx
), the
corresponding
TRSn
bit is cleared after the message is successfully sent or if
the transmission is aborted due to a lost arbitration or an error frame on
the CAN bus line. Thus, there is no further attempt to transmit the mes-
sage again if the initial try failed, and the abort error is reported (
AAn
=
1
in
CAN_AAx
)
Auto-Transmission
In auto-transmit mode, the message in mailbox 11 can be sent periodically
using the universal counter. This mode is often used to broadcast heart-
beats to all CAN nodes. Accordingly, messages sent this way usually have
high priority.
The period value is written to the
CAN_UCRC
register. When enabled in this
mode (set
UCCNF[3:0]
=
0x3
in
CAN_UCCNF
), the counter (
CAN_UCCNT
) is
loaded with the value in the
CAN_UCRC
register. The counter decrements at
the CAN bit clock rate down to 0 and is then reloaded from
CAN_UCRC
.
Each time the counter reaches a value of 0, the
TRS11
bit is automatically
set by internal logic, and the corresponding message from mailbox 11 is
sent.
For proper auto-transmit operation, mailbox 11 must be configured as a
transmit mailbox and must contain valid data (identifier, control bits, and
data) before the counter first expires after this mode is enabled.
Receive Operation
The CAN hardware autonomously receives messages and discards invalid
messages. Once a valid message has been successfully received, the receive
logic interrogates all enabled receive mailboxes sequentially, from mailbox
23 down to mailbox 0, whether the message is of interest to the local node
or not.
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...