Can Frame Formats; Data Frames - Infineon Technologies TC1728 User Manual

returns to idle state. Therefore, the same identifier can be sent in a Data Frame only by
one node in the system. There must not be more than one node programmed to send
Data Frames with the same identifier.
Standard message identifier has a length of 11 bits. CAN specification 2.0B extends the
message identifier lengths to 29 bits, i.e. the extended identifier.
20.1.2

CAN Frame Formats

There are three types of CAN frames:
•

Data Frames

• Remote Frames
• Error Frames
A Data Frame contains a Data Field of 0 to 8 bytes in length. A Remote Frame contains
no Data Field and is typically generated as a request for data (e.g. from a sensor). Data
and Remote Frames can use an 11-bit "Standard" identifier or a 29-bit "Extended"
identifier. An Error Frame can be generated by any node that detects a CAN bus error.
20.1.2.1 Data Frames
There are two types of Data Frames defined (see
• Standard Data Frame
• Extended Data Frame
Standard Data Frame
A Data Frame begins with the Start-Of-Frame bit (SOF = dominant level) for hard
synchronization of all nodes. The SOF is followed by the Arbitration Field consisting of
12 bits, the 11-bit identifier (reflecting the contents and priority of the message), and the
RTR (Remote Transmission Request) bit. With RTR at dominant level, the frame is
marked as Data Frame. With RTR at recessive level, the frame is defined as a Remote
Frame.
The next field is the Control Field consisting of 6 bits. The first bit of this field is the IDE
(Identifier Extension) bit and is at dominant level for the Standard Data Frame. The
following bit is reserved and defined as a dominant bit. The remaining 4 bits of the
Control Field are the Data Length Code (DLC) that specifies the number of bytes in the
Data Field. The Data Field can be 0 to 8 bytes wide. The Cyclic Redundancy (CRC) Field
that follows the data bytes is used to detect possible transmission errors. It consists of a
15-bit CRC sequence, completed by a recessive CRC delimiter bit.
The final field is the Acknowledge Field. During the ACK Slot, the transmitting node
sends out a recessive bit. Any node that has received an error free frame acknowledges
the correct reception of the frame by sending back a dominant bit, regardless of whether
or not the node is configured to accept that specific message. This behavior assigns the
User's Manual
MultiCAN, V2.24
Controller Area Network Controller (MultiCAN)
Figure
20-3
20-1):
V1.0, 2011-12
TC1728