Chapter One
Product Overview
The EM00-GATE-0000 is a gateway / bridge that allows up to 32 Watlow controllers to be directly connected to an Ethernet network. Using an HTTP Browser such as Microsoft Internet Explorer or Netscape Navigator you may access 16 controllers and view several controllers’ parameters via an onboard Web (HTTP) server.
Ethernet Gateway
The Ethernet gateway provides a means for monitoring and configuring runtime parameters of multiple controllers via a web browser. The gateway is also a bridge for Modbus messages between the Ethernet bus and EIA-485 or EIA-232 links. The Gateway supports full product configuration; monitoring and configuration of runtime parameters via MODBUS TCP over TCP/IP using a software package such as Watview sold by Watlow.
Ethernet Gateway Architecture
This product has three physical connectivity points to the physical world. They are the serial (EIA-485 or EIA-232), Ethernet port (10BaseT), and the power supply pins.
The EIA-485 / EIA-232 connection supports Modbus RTU protocol and operates as a Master port. It will initiate data read/write requests to supported standard Watlow controllers. There exists a virtual image of the controller’s data points in the gateway. The polling engine that initiates the Modbus RTU requests is responsible for synchronization of the virtual image and the actual controller. Changes to control data occur both at the controller and at the virtual image.
The 10BaseT connection supports the TCP/IP stack. At the application layer it has an HTTP (web) and Modbus server. The HTTP server will provide current controller status from the virtual image via HTML. The HTTP server provides a means of changing some runtime parameters via HTML. The TCP/IP stack supports DHCP client, AutoIP, static IP, DNS client, and Netbios name resolution. The 10BaseT connector is an RJ45 per the IEEE 802.3 specification.
The EM00-GATE-0000 can be used as a bridge for Modbus RTU messages. This is concurrent with all other communicating functions. In this scenario, the gateway simply passes the request that comes in on the Ethernet connection through to the EIA-485 or EIA-232 connection. When the response is returned from the controller, it is sent back on the Ethernet connection. No processing of the packet contents is necessary to bridge the two physical layers.
Block Diagram of Gateway
| PowerSource | | |
| | Modbus | | Modbus |
| | TCP/IP | |
| | | RTU |
EtherNet | TCP/IP | | |
TFTP | GATEWAY | |
| | Client | | |
| | WEB | Virtual | Poll |
| | Server | Engine |
| | Image |
| | | |