The workspace maintains the configuration information for each Modbus (e.g., the latency time for critical broadcasts, the devices assigned to each network, the broadcast signals that traffic each network, etc.). You can access the network configuration by right-clicking on a logical network icon in the workspace and selecting the Properties item from the drop-down menu.
General Info Screen
Figure 9.25. Modbus Configure Network Dialog General Info Panel
Network Name is the physical name for the network within this Design Pad workspace.
Interface gives the full name including HWI file name, NIM name and network layer for the source or destination of data on the network.
Station ID identifies which station number the interface named to its left resides upon.
Station Type identifies / selects the device as a master or slave. Click on the cell to change the setting. Note that there can be only one master on a Modbus network.
Modbus Settings Screen
Figure 9.26. Modbus Configure Network Settings Panel
The following features are accessible from the Modbus Settings dialog:
Transmission mode may be set to Binary (RTU) or ASCII. Binary mode transmits each byte as a hexadecimal number, while ASCII messaging encodes messages into ASCII character codes.
Minimum Receive to Transmit Delay is the number of milliseconds between receipt and transmission of messages. More messaging might require a longer delay.
If a Fairmount Automation product is master of the network, the Master Polling Table tell the master all of the messages that will should occur when the network is deployed. Each entry in the table contains the following information:
Source Device identifies the device sending the data. Station IDs identify non-master devices.
Destination Device identifies which device receives the data the source device transmits. Station IDs identify non-master devices. Note that the Master (as defined in the Modbus specification) must be either the source or destination device.
Data Type identifies whether the data is binary (a coil) or analog (a register).
Source Addr is the starting ID register / coil in the Source Device involved with the transaction.
Dest Addr is the starting ID register / coil in the Destination Device involved with the transaction.
Num of Points indicates the number of register or coil items to transfer (beginning at the starting ID) in this network transaction. In each device involved in the message, the data transfer will start at the starting ID register / coil (defined above) and read / write the number of resisters or coils defined by this parameter.
Period (ms): The periodic rate (in milliseconds) at which this message should occur.
Timeout (ms): The amount of time (in milliseconds) allowed to pass from the last occurrence of this message before a network error is called.
Use the buttons to the right of the dialog to add, remove, and/or edit within the table. Also, addresses in the Polling table may be displayed in decimal or hexadecimal.
Signals Screen
Figure 9.27. Modbus Configure Network Signals Panel
The Signals dialog summarizes all of the signals on the Modbus network as defined via Design Pad.
Name identifies the transmission type (coil or register) and its unique signal ID within that type.
Source Station ID identifies on the Modbus network device address where the data transmitted originates.
Type indentifies whether the data is digital or analog.
Critical? is reserved for future use (i.e. not current used and set to no).
Latency show the desired period transmission rate (in milliseconds)
0% Map identifies the equivalent floating point value that is equal to a 16 bit Modbus register value of 0x0000 (note for coil/digital types this row is N/A and always set to 0).
100% Map identifies the equivalent floating point value that is equal to a 16 bit Modbus register value of 0xFFFF (note for coil/digital types this row is N/A and always set to 1).
Note: The controllers will map a 32 bit IEEE floating point value into a 16 bit register transmission / reception using the 0% and 100% map as the end points and a linear interpolation in-between.
Initial value is that value to which the data item is set so it has a defined value upon its first transmission even if not yet set by the schema logic.
