QD1 IO Expansion Module User Manual
8 Document Version V3.0 (2020-08-18)
Chapter 2 Work Principle
QD1 products communicate as slave stations with master stations (such as
computers, controllers, etc.) via Modbus TCP. You can load library functions and header
files from folder into program using Microsoft Visual Studio and call related functions to
read and write QD1.
QD1 supports two data types: DI and DO.
DI is a discrete input, in which each address corresponds to one data bit, and users
can only read its status, but cannot modify it.
DO is a coil output, in which each address corresponds to one data bit, and users
can set, reset, and read back its status.
2.1 Communication networking
QD1 supports Modbus TCP protocol communication. Main controller can access
and control each IO channel upon connection to QD1 with network cable; QD1 module
has dual RJ45 ports and native routing & forwarding function for free forwarding at
10/100 M network, and can flexibly communicate with main controller via cascade
communication or daisy chain topology. The diagrams of typical networking and free
networking are shown in Figure 2-1 andFigure 2-2, respectively: