Shanghai ZLAN Information Technology Co., Ltd Tel: +86-17321037177 http://www.zlmcu.com
42
5. Work Mode and Transfer Protocol
Different application can choose different work mode and transfer protocol of serial device
server to be more stable and reliable.
The use of serial device server is basically divided into two kinds: virtual serial port and
non-virtual serial port, respectively, as shown in figure 21 TCP communication diagram and
figure 24 virtual serial port use. The virtual serial port mode needs the connected user
software is COM port, as user software and user device are serial ports; in Non-virtual serial
port mode user software is direct TCP/IP communication but user device is still serial port.
In the non-virtual serial port mode, the
“Transfer Protocol” have 3 mode of transparent
transmission, Modbus TCP to RTU and Realcom protocol. If the user software is fixed
protocol Modbus TCP protocol and the lower computer is Modbus RTU, choose the Modbus
TCP to RTU mode. Realcom protocol currently only use in when multi-port serial device
server as TCP Client to connect one Server and the Server use virtual serial port.
The usage is summarized as follows:
Table 6 Network Configuration Mode
No
Virtual Serial
Port Use
Device Work
Mode
Transfer
Protocol
Instruction
1
Use
TCP Server
None
Suitable for user software to
open COM port to actively collect
data.
2
Use
TCP Client
None
Suitable for device actively send
data, if choose TCP Server it
may have the problem that
device cannot reconnect after
broken.
3
No use
TCP Server
Modbus TCP to
RTU
Suitable for that the user
software is Modbus TCP and
user device is Modbus RTU, as
well the Modbus TCP is main
station.
4
No use
TCP Client
Modbus TCP to
RTU
Suitable for user software is
Modbus TCP and user device is