LM3S5737 Datasheet, PDF (615/833 Pages) Texas Instruments – Stellaris® LM3S5737 Microcontroller

Stellaris® LM3S5737 Microcontroller
Table 16-1. Controller Area Network Signals (100LQFP) (continued)
Pin Name
Pin Number Pin Type Buffer Type^a Description
CAN0Tx
11
O
TTL
CAN module 0 transmit.
a. The TTL designation indicates the pin has TTL-compatible voltage levels.
16.3
Functional Description
The Stellaris CAN controller conforms to the CAN protocol version 2.0 (parts A and B). Message
transfers that include data, remote, error, and overload frames with an 11-bit identifier (standard)
or a 29-bit identifier (extended) are supported. Transfer rates can be programmed up to 1 Mbps.
The CAN module consists of three major parts:
■ CAN protocol controller and message handler
■ Message memory
■ CAN register interface
A data frame contains data for transmission, whereas a remote frame contains no data and is used
to request the transmission of a specific message object. The CAN data/remote frame is constructed
as shown in Figure 16-2 on page 615.
Figure 16-2. CAN Data/Remote Frame
Start
Of Frame
Remote
Transmission
Request
Bus
Idle
S
O
F
Message Delimiter
R
T
R
Control
Field
Data Field
Delimiter
Bits
CRC
A
Sequence ^C
K
EOP IFS ^Bus
Idle
Number ₁
Of Bits
11 or 29
16
0 . . . 64
15 1 1 1
7
3
Arbitration Field
CRC Sequence
CRC
Field
End of
Frame
Field
Interframe
Field
Bit Stuffing
CAN Data Frame
Acknowledgement
Field
The protocol controller transfers and receives the serial data from the CAN bus and passes the data
on to the message handler. The message handler then loads this information into the appropriate
message object based on the current filtering and identifiers in the message object memory. The
message handler is also responsible for generating interrupts based on events on the CAN bus.
The message object memory is a set of 32 identical memory blocks that hold the current configuration,
status, and actual data for each message object. These are accessed via either of the CAN message
object register interfaces.
November 17, 2011
615
Texas Instruments-Production Data