Specifications

Overview Ethernet
Quick Start Guide for the MELSEC STlite Series 4 - 1
4Ethernet
4.1 Overview
Ethernet is unrivalled for the widest possible set of connectable technologies. While being well estab-
lished in the office and IT environments, its adoption into automation environments is both rapid and
broad ranging.
Ethernet is a platform for a very wide range of data communications protocols. The combination of
Ethernet and the extremely widespread TCP/IP protocol enables high-speed data communications
between process supervision and the PLC.
There is also a growing demand for Ethernet to be used as a peer-to-peer network.
4.2 Head Station STL-ETH1 (Ethernet)
The head station STL-ETH1 connects the MELSEC STlite modules to the Ethernet fieldbus system. The
STL-ETH1 can be used for widespread solutions in the field of factory automation.
Equipped with two RJ-45 ports, which both work as 2-channel switches, the head station enables easy
and cost-effective cabling such as linear bus topology for which no additional external switches or
hubs are required.
With the DIP switch the last byte of the IP address, as well as the assignment of the IP address (DHCP,
BootP, firm setting) can be given.
In the head station, all input signals from the sensors are combined. After connection, the head station
determines which I/O modules are on the node and creates a local process image from these. Analog
and special function module data is sent via words and/or bytes; digital data is grouped bit-by-bit.
The local process image is divided into two data zones containing the data received and the data to
be sent.
The data of the analog modules is mapped first into the process image. The modules are mapped in
the order of their physical position after the head station.
The bits of the digital modules are combined into words and then mapped after the analog ones in the
process image. If the number of digital I/Os is greater than 16 bits, the head station automatically
begins a new word.
All sensor input signals are grouped in the head station (slave) and transferred to the higher-order
controller (master) via the fieldbus. Process data linking is performed in the higher-order controller.
The higher-order controller puts out the resulting data to the actuators via the bus and the node.
The fieldbus connection consists of two ports (RJ-45). An Ethernet switch integrated in the head sta-
tion operates in the store and forward mode.
Fig. 4-1: Head station STL-ETH1 for Ethernet
(with connected digital input
module)