FeMODBUS

The user can define tags and map them to any register on the local computer. The tags can be: read or write. The tags are available to other DDE clients with the format: "MB|TAGS|TagName", where "MB" is the DDE_Application name, and "TAGS" is the DDE_Topic name of the program. If a tag is "read", it will take the value of the register that was mapped to, in the remote server registers, and will be sent to any DDE client that wants to read the tag through a DDE message. If the tag is "write" it will change the value of the register that is mapped to, in the case the tag was changed by a DDE client.

The program is a client that can connect with other Modbus servers over the Ethernet network, with TCP/IP. Once the servers are defined in the remote servers list, the program will reserve, for any server connection, 800 registers (200 for each of the modbus register types: coils, digital inputs, input registers, and holding registers). For every server the user can add multiple requests. A request is a command to: "read" – one or multiple coils, discrete inputs, input registers or holding registers, "write" – one or multiple coils or holding registers. In this way the user can map the registers from the remote server in any register from the local computer.

The program is designed to be a Modbus server over the Ethernet network, TCP/IP, with 800 registers. It can support up to 16 TCP/IP connections (modbus clients). If another modbus client is connecting to the local computer's IP address, on port 502 (or the port set up in configuration), and is sending a request, the program will send back the registers values, or it will write the new values in the local registers of the TCP/IP modbus server. These registers, of the local modbus server, can be mapped to tags. And the tags values can be read/changed with DDE messages from other DDE clients.

A second important feature of this modbus server is that it can act as a "bridge" between the TCP/IP network and a local serial COM line, defined by the user. In this case, if a client is sending a TCP/IP request for a modbus address different than 255, then the program will send the request on the local serial line, and will send back the answer, on the TCP/IP connection. In this way the local modbus server can act as a "bridge" Modbus TCP/IP to Modbus RTU.

The program is an RTU modbus server over a local serial COM line, defined by the user. There are 800 registers allocated for the RTU modbus sever. As with the TCP/IP server, the registers for the RTU modbus server can be mapped to different tags. These tag values can be read/changed by other DDE clients, with DDE messages. The RTU server address can be set by the user to any number 1...254.