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22
Byte 0 1
2 3 4-7 8-15
Description 0xFF
Number of data
contained in
CAN frame
Sequence
number
Reserved
Frame
header and
CAN frame
CAN frame
data

Byte definition description in PROFINET IO
1. Byte0 - Byte3 are control bytes
If the byte0 is zero, it means that the CAN frame of this sequence number is sent once; If the byte0 is not zero, it
means that all CAN frames of this sequence number are sent periodically, The sending cycle is determined by the
value of byte0, the sending cycle = the value of the byte0 * 10ms. For example, if the value of the byte0 is 10, the
sending cycle is 100ms.
Byte 1, the number of data contained in the CAN frame, ranging from 0 to 8.
Byte 2, the sequence number. The initial value of the sequence number in the output frame is not zero. If it is
single transmission mode, it must be increased by 1 every time a new frame is sent. In this way, the gateway treats
this frame as a new single transmission data. The sequence number will become 0 if it reaches 255 and increase by
1. If the CAN frame is sent periodically, the sequence number may not be increased by 1.If you want to switch
from single transmission mode to repeated transmission mode, the sequence number needs to be increased by 1,
and the 0th byte is a non-zero value; if you want to switch from repeated transmission mode to single transmission
mode, the sequence number needs to be increased 1, and the 0th byte is 0;
2. Byte4 - Byte7 are CAN frame header and CAN frame mode control (29bit CAN ID)
The format of the byte4 is as follows:
Bit Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
Description Reserved RTR Reserved The highest 5 bits of the frame header
Bit6 of the byte4: RTR. If RTR is 0, it means data frame, if it is 1, it means remote frame.
Bit0-Bit4 of the byte4, to the byte7, are the frame header of CAN2.0A/2.0B.
Byte5:
Bit Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
Description The second highest 8 bits of the frame header