Chengdu Ebyte Electronic Technology Co., Ltd.
ME31- XAXA0404 _User Manual
Copyright © 2012–2023 , Chengdu Ebyte Electronic Technology Co., Ltd.
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4.3 Modbus gateway
The device can transparently transmit non-native Modbus commands from the network/serial port to the serial
port/network, and the local Modbus commands are directly executed .
4.3.1 Modbus TCP/RTU protocol conversion
After opening, Modbus TCP data on the network side will be converted to Modbus RTU data .
4.3.2 Mod bus address filtering
This function can be used as the host to access the serial port of the device in some host software or
configuration screen, and use the gateway function of the device, the slave is on the network end, and Modbus is
turned on It is used when the function of TCP to RTU is converted. There are multiple slaves on the bus that may
cause data confusion. At this time, enabling address filtering can ensure that only the specified address can pass
through the device; when the parameter is 0, the data is transparently transmitted, and the parameter is 1-255 Only
data from the set slave address is passed.
4.3.3 Mod bus TCP protocol data frame description
TCP frame format:
Transaction ID
Protocol ID
length
device address
function code
data segment
2 Bits
2 Bits
N+ 2 B it
1 Bit
1 B it
N B it
Transaction ID: It can be understood as the serial number of the message. Generally, 1 is added after each
communication to distinguish different communication data messages .
Protocol identifier: 00 00 means Modbus TCP protocol.
Length: Indicates the length of the next data in bytes.
Example: Get D I Status
0 1 00
0 0 00
0 0 06
0 1
0 2
0 0 00 00 04
Transaction ID
Protocol ID
length
device address
function code
data segment
4.3.4 Mod bus RTU protocol data frame description
RTU frame format:
device address
function code
data segment
Check codeCRC
1 bit
1 B it
N B it
2 Bits
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