Introduction.
The tSH-730 series allows two masters to communicate with the same slaves via serial RS-232/485, even at different speeds. Mobus/RTU, Modbus/ASCII, DCON or custom protocol is supported.
2x Master, why?
In an RS-232 or RS-485 serial network, there will normally be one Master and several Slaves. It is the Master that decides which Slave will act and respond to the command sent by the Master. But with this new device from ICPDAS, the tSH-730 series, it is now possible to have two Masters at the same time.
The two Masters will be able to communicate with the same Slaves, for example if you have a control display at each end of a room that controls the lights or something else. It could also be that Master 2 runs as a backup, so if Master 1 stops, Master 2 takes over.
Another application may be that you have two Masters and several Slaves but want to use the same RS-485 network you have wired up. One Master is then set up to communicate with selected Slaves, the other Master is set up to communicate with the other Slaves.
But how?
When two masters normally communicate on the same connection, at the same time, data will be lost. We therefore need a buffer and that's exactly what our tSH-730 series is. In the visual figure above, there are 2 masters, Master 1 sends red packets and Master 2 sends green packets.
When Master 1 sends a red packet, it is forwarded to the salvos, the selected slave responds and the response is sent to Master 1. Likewise with Master 2.
But when Master 1 and Master 2 send data at the same time, we need to delay one signal. In the example above, the red packet is sent out to the slaves, while the green packet is stored for a moment.
The response to the red packet is sent back to Master 1, then the green saved packet can be sent to the slaves and the response to it, back to Master 2, without anyone noticing anything.
Note - however, it is important that you can set a longer response timeout in the two Masters, as the responses may be delayed while waiting to go through the converter. It is also important that Master 1 and Master 2 do not use the 100% bandwidth, there must be room for both at the same time.
Modbus/RTU, Modbus/TCP, DCON or your own protocol.
All Slaves must run at the same speed, but the two Masters can run at different speeds and do not need to be the same speed as the Slaves.
During configuration of the module, which is easily done via the built-in Ethernet connector, you first choose which protocol and speed Master 1 should run, then Master 2 and finally the Slaves. The protocols supported are the popular Modbus/RTU and Modbus/ASCII, ICPDAS’ DCON (I-7000 series) or your own protocol (Raw data/text mode).
How can I find out more (useful links)?
- Yes please, please contact me for more information (sent as email)
- Call us on 4485 8000