PLX30 Series
MBTCP Protocol
Ethernet and Serial Gateways
User Manual
ProSoft Technology, Inc.
Page 95 of 200
September 19, 2012
Modbus TCP/IP Server
The server driver accepts incoming connections on Service Port 502 for
Clients using Modbus TCP/IP MBAP messages and connections on Service
Port 2000 (or other Service Ports) for Clients using Encapsulated Modbus
messages.
Supports multiple independent server connections for any combination of
Service Port 502 (MBAP) and Service Port 2000 (Encapsulated)
Up to 20 servers are supported
Modbus Commands
Supported
(Client and Server)
1: Read Coil Status
2: Read Input Status
3: Read Holding Registers
4: Read Input Registers
5: Force (Write) Single Coil
6: Preset (Write) Single
Holding Register
15: Force (Write) Multiple
Coils
16: Preset (Write) Multiple
Holding Registers
Configurable
Parameters:
(Client and Server)
Gateway IP Address
PLC Read Start Register (%MW)
PLC Write Start Register (%MW)
Number of MBAP and MBTCP servers
Gateway Modbus Read Start Address
Gateway Modbus Write Start Address
Configurable
Parameters:
(Client Only)
Minimum Command Delay
Response Timeout
Retry Count
Command Error Pointer
Command List
Up to 160 Modbus commands (one tag per command)
Status Data
Error codes reported individually for each command.
High-level status data available from Modbus TCP/IP
Client (for example PLC)
Command List Polling
Each command can be individually enabled or disabled;
write-only-on-data-change is available
6.1.2 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 communication port.
In addition to data from the Client and server, status and error information
generated by the gateway can also be mapped into the internal database.
Modbus TCP/IP Client Access to Database
The Client functionality exchanges data between the PLX30 gateway'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,
specifies what data is to be transferred between the gateway 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.
