Pentax DSI-200 Series User Manual page 152

Modbus Communication Protocol
The drive provides RS485 communication interface and supports
Modbus-RTU communication protocol so that the user can
implement centralized control, such as setting running commands
and function codes, and reading running status and fault
information of the AC drive, by using a PC or PLC.
J.1 Agreement content
This protocol defines content and format of transmitted messages
during serial communication, including master polling (or
broadcasting) format and master coding method (function code for
the action, transmission data, and error check). The slave uses the
same structure in response, including action confirmation, data
returning and error check. If an error occurs when the slave
receives a message, or the slave cannot complete the action
required by the master, the slave returns a fault message as a
response to the master
Application
The AC drive is connected to a "single-master multi-slave"
PC/PLC control network with RS485 Bus.
Bus Structure
(1) Topological structure
The system consists of a single master and multiple slaves. In the
network, each communication device has a unique slave address.
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