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Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 564
UG585 (v1.11) September 27, 2016
Chapter 18: CAN Controller
Reads
Data starts at byte 0 and continues for the number of counts in DLC. Software should read both data
words, but the only valid bytes are determined by DLC.
Table 18-3 provides bit descriptions for the identifier word bits, the DLC word bits, and data word 1
and data word 2 bits.
Table 18-3: CAN Message Word Register Bit Fields
Bits Name
Default
Value
Description
Identifier Word
31:21 ID[28:18] 0
Standard Message ID
The identifier portion for a standard frame is 11 bits.
These bits indicate the standard frame ID.
This field is valid for both standard and extended frames.
20 SRR/RTR 0
Substitute Remote Transmission Request
This bit differentiates between data frames and remote
frames. Valid only for standard frames. For extended
frames this bit is 1.
1: Indicates that the message frame is a Remote Frame.
0: Indicates that the message frame is a Data Frame.
19 IDE 0
Identifier Extension
This bit differentiates between frames using the Standard
Identifier and those using the Extended Identifier. Valid
for both Standard and Extended Frames.
1: Indicates the use of an extended message identifier.
0: Indicates the use of a standard message identifier.
18:1 ID[17:0] 0
Extended Message ID
This field indicates the extended identifier. Valid only for
extended frames.
For standard frames, reads from this field return 0s.
For Standard frames, writes to this field should be 0s.
0RTR0
Remote Transmission Request
This bit differentiates between data frames and remote
frames.
Valid only for extended frames.
1: Indicates the message object is a remote frame.
0: Indicates the message object is a data frame.
For standard frames, reads from this bit returns 0.
For standard frames, writes to this bit should be 0.
DLC Word
31-28 DLC 0
Data Length Code
This is the data length portion of the control field of the
CAN frame. This indicates the number valid data bytes (0
to 8) that are in the Data Word 1 and Data Word 2
registers.