Little known fact: SCADAPacks can act as a Modbus Store and Forward hub when configured properly. Lesser known fact: SCADAPacks will also Store and Forward Enron Modbus, ROC Protocol, or basically any communications protocol where the first byte of the message is the address, has messages less than 240 bytes and uses Modbus CRC for checking message integrity. Even lesser known fact: Store and Forward will play nice and work with MSTR and MSIP polling blocks used in logic… provided there is some dead-time between the MSTR polls for Store and Forward to use.
- You have a single radio on a remote location but there are some other Modbus devices connected to the SCADAPack. Instead of doing complicated Modbus MSTR polling with Telepace logic, you could configure Store and Forward so SCADA hosts could read messages from the SCADAPack and the connected equipment.
- Radio repeaters… you have a remote location with a good connection to a SCADA host. Near this remote location is another site that has a poor or no connection to the SCADA host. You could set up a small point-to-point radio system between the two remote sites and use Store/Forward to pass SCADA host messages through to the site with no communications. This also allows the site with good communications to have a link to the other site, which might be useful for control (pipeline segments).
- Ethernet-to-serial conversion. You can use the SCADAPack as a remote Ethernet to Serial converter by enabling Store and Forward. This would enable access to other devices as well, such as Floboss flow computers.
- Direct to EFM connections for audit data collection. Here you could enable store and forward to pass through audit data requests direct to the EFM’s behind the SCADAPack. These EFMs would need to support Modbus or ROC protocol but this allows the SCADAPack to poll the EFM for current data to control with while allowing a SCADA host or EGM software access to the EFM directly.
Configuring the Store and Forward settings is quite simple.
- Enable Store and Forward on the ports you want to use.
Here is a look at enabling Store and Forward on a serial port:
And here is the setting on an Ethernet or IP Port:
- Add some Store and Forward Rules to the Store and Forward table in Telepace.
You can make a SCADAPack listen for a particular address and then forward to a different address. However, most people just pass through and keep the addresses the same as it can get confusing if the addresses are all different.
Note: You do not need to configure ‘reverse’ rules in order to have two-way communications. You only need to specify where the master messages are coming from and which interface to send them to. The SCADAPack knows that it needs to send responses from the remote slave back to the correct interfaces.
Look forward to hearing from people about other possible use-cases for these settings. Connect with me on LinkedIn and let the discussions begin!