CANFDNET-400U
High-performance Four-channel CANFD Bus-to-Ethernet Converter User Manual
©2021 Guangzhou ZLG Microelectronics Technology Corp.,Ltd.
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User Manual
contains the frame representation of 8 bytes of valid data (0x11, 0x22, 0x33, 0x44, 0x55,
0x66, 0x77, 0x88)
0x8
8
0x1
2
0x3
4
0x5
6
0x7
8
0x1
1
0x2
2
0x3
3
0x4
4
0x5
5
0x6
6
0x7
7
0x8
8
Table 4.24 Example of CAN format conversion standard frame
The following example is a CAN standard data frame. The ID is 0x3FF, frame
representation containing 6 bytes of valid data (0x11, 0x22, 0x33, 0x44, 0x55, 0x66)
0x0
6
0x0
0
0x0
0
0x0
3
0xF
F
0x1
1
0x2
2
0x3
3
0x4
4
0x5
5
0x6
6
0x0
0
0x0
0
4.4 Modbus Conversion
The Modbus protocol is a standard application layer protocol, which is widely
used in various industrial control scenarios. The protocol is open, real-time, and has a
good communication verification mechanism. It is ideal for scenarios with high
communication reliability requirements.
The converter uses the standard Modbus RTU protocol format on the serial port
side.Therefore, the converter not only allows you to use the Modbus RTU protocol,
but the converter can also directly interface with other devices that support the
Modbus RTU protocol.
On the CAN (CANFD) side, an easy-to-use segmented communication format is
developed to realize Modbus communication. The role of the converter is still protocol
verification and forwarding. It supports Modbus protocol transmission, not Modbus
master or slave host. The user can communicate according to the Modbus protocol.
Note: In this conversion mode, the preset CAN (CANFD) ID is invalid, because
the identifier (frame ID) sent at this time is filled with the address field in the Modbus
RTU serial frame.
4.4.1 Frame Formats
1. Serial bus frame
The serial interface adopts the standard Modbus RTU protocol, so the user frame
only needs to conform to this protocol. If the transmitted frame does not meet the Modbus
RTU format, the converter discards the received frame without converting it.
The Modbus RTU transmission format adopted by the converter is 1 start bit, 8 data
bits, and 1 stop bit. The maximum length of the Modbus RTU frame is the buffer length:
5,000 bytes.
2. CAN (CANFD) bus frame
If the device on the CAN (CANFD) side adopts the Modbus protocol, a reliable
transmission format needs to be defined for it. A segmentation protocol is used here,
which defines a method for segmenting and reorganizing information whose length is
greater than the maximum data length of a CAN (CANFD) message.
The formulation of the segmented transmission protocol refers to the transmission
protocol of segmented messages in DeviceNet. For CAN messages, the segmented
