ProSoft Technology 5201-MNET-ASCII - Manual (Page 13)

MNET ♦ ProLinx Gateway Functional Overview
Modbus TCP/IP Interface Module Driver Manual
ProSoft Technology, Inc. Page 13 of 78
September 1, 2010
1.4 Internal Database
Central to the functionality of the gateway is the internal database. This database
is shared between all the ports on the gateway and is used as a conduit to pass
information from one device on one network to one or more devices on another
network. This permits data from devices on one communication port to be viewed
and controlled by devices on another port.
In addition to data from the Server and Client ports, status and error information
generated by the gateway can also be mapped into the internal database.
1.4.1 Modbus TCP/IP Client Access to Database
The client functionality exchanges data between MNET module's internal
database and data tables established in one or more Quantum processors or
other server based devices. The command list, defined in the user configuration,
defines what data is to be transferred between the module and each of the
servers on the network. No ladder logic is required in the processor (server) for
client functionality, except to assure that sufficient data memory exists.
The following illustration describes the flow of data between the Ethernet clients
and the internal database.
1.4.2 Modbus TCP/IP Server Access to Database
The MNET gateway provides server functionality using reserved Service Port
502 for Modbus TCP/IP MBAP messages, as well as Service Ports 2000 and
2001 to support the TCP/IP Encapsulated Modbus version of the protocol used
by several HMI manufacturers. Server support in the gateway permits client
applications (that is, HMI software, Quantum processors, and so on) to read from
and write to the gateway’s database. This document discusses the requirements
for attaching to the gateway using client applications.