How can several SCADA hosts get the simultaneous access to the same Modbus RTU devices using a single gateway?

Although the gateway can deal with this task, remember that the serial port bandwidth remains unchanged. If several requests are received through a single serial port, a delay may occur, as the gateway processes the earlier requests first. So, if you want to allow several masters to simultaneously access a Modbus RTU device, you need to choose the proper polling time first.

Although the gateway can deal with this task, remember that the serial port bandwidth remains unchanged. If several requests are received through a single serial port, a delay may occur, as the gateway processes the earlier requests first. So, if you want to allow several masters to simultaneously access a Modbus RTU device, you need to choose the proper polling time first.

Nevertheless, the above given solution is not the only one. MGate MB3660 supports the "agent" mode that actively and constantly receives data from the connected devices.

The updating data is stored in the internal memory, which is used to respond to the host requests. Although this solution is faster and more efficient, the obtained data will not be the most relevant.

For instance, if one request lasts 100 ms, then 5 connections will cause a delay of at least 100 ms х (5-1) = 400 ms before sending the next request. This means that the polling cycle of each SCADA host should equal to 400 ms (plus some tolerance).