Address Blocking / Translation
If the SS20 is installed at the slave end of a polled network such as a broadcast radio network it is important to set the SS20 to block any addresses that appear on the network that are not attached downstream of the SS20's output port. Enabling the `Block all other addresses` checkbox can be used to block all the Modbus or ROC addresses except for ones specifically passed in the table.
Address Translation is used to convert an incoming message for a specific Modbus address to a different Modbus address, the SS20 will convert the incoming message to the new address and automatically convert the address of the returned response back to the original address. Address Translation is valid only for Modbus protocol messages whereas blocking and passing are applicable for any protocol where the address is the first byte of the message such as Fisher ROC protocol.
The Broadcast checkbox tells the SS20 to block response messages from requests sent for the incoming address specified. It can be used to send write commands to multiple RTU's simultaneously for time synch or shutdown type functions.
| Enable Address Translation / blocking | Enable Address Translation/Blocking for the specified input port. |
| Block All Other Addresses | Enabling the `Block all other addresses` checkbox can be used to block all the incoming Modbus or ROC addresses except for ones specifically passed or translated in the table. 1) |
| Add | Add a new Translation/Blocking rule to the table. |
| Remove | Remove the selected rule from the table. |
| Incoming | Incoming address received at the input port. |
| Action | Drop down box selects the action to be performed by the SS20 for messages containing the address specified in the “Incoming” column. Options are Translate, Blocked, or Passed. If “Translate” is selected the SS20 will translate messages with the address specified in the “Incoming” column to the address specified in the “Outgoing” column before transmitting the message out the output port. The SS20 will then translate the response message for that transaction when received by the output port back to the original address before relaying the response back to the input port. 2) If “Blocked” is selected in the table the SS20 will prevent messages containing the address specified in the “Incoming” column from passing through the SS20 regardless of the state of the “Block all other addresses” checkbox. If “Passed” is selected in the table, the SS20 will forward messages containing the address specified in the “Incoming” address to the output port unchanged. |
| Outgoing | When ”Translate” is selected under the “Action” column, the SS20 will convert messages received with the address specified in the “Incoming” column to the address specified in the “Outgoing” column. |
| Broadcast | If the “Broadcast” Checkbox is checked the SS20 will send the incoming message out the output port, however it will block the returning response message and not return the response to the input port. This feature can allow the host to send a write command to multiple devices simultaneously over a multipoint network without the responses of all the devices receiving the message colliding and jamming up the network on return. This is useful for messages such as time synchronization messages or global shutdown commands and when used in combination with the translation functions, multiple different broadcast groups can be configured on different broadcast addresses for different types of devices on mixed networks. |
