Filter
Top Products
C
section level 1 1
figure_ap level 1
table_ap level 1
C-1
GFK-0804B
Appendix C RTU Protocol
This appendix describes the Remote Terminal Unit (RTU) serial communications
protocol, which can be used to provide communications between the Micro PLC or other
remote device and a host computer.
Message Types
Transmission Sequence
Message Fields
Character Format
Message Termination
Timeout Usage
Cyclic Redundancy Check (CRC)
RTU Message Length
RTU Table Addresses
Message Descriptions
Communication Errors
Refer to appendix E for a sample RTU master program.
Introduction
One of the software Setup parameters for the Micro PLC is the selection of either Micro
PLC protocol or RTU protocol. RTU protocol must be selected to use the features
described here.
RTU protocol is a query–response protocol used for communication between devices,
such as the Micro PLC and a host computer. The host computer operates as the master
device; the Micro PLC is always a slave.
The data transferred consists of 8–bit binary characters with a parity bit. No control
characters are added to the data block; however, an error check (Cyclic Redundancy
Check) included as the final field of each query and response to ensure accurate trans-
mission of data.