SCADAPack535E to utilize 3 RS-232 Serial Port for Modem and Radio communication

[LeeWaiLip]

Dear Expert,

I currently come across a project that the customer have purchased the SCADAPack535E and request us to integrate the SCADAPack535E with the existing 1 unit of Siemens 3G modem and 2 unit of Tait analog radio. As of all 3 modem and radio required serial RS-232 interface, hence we need to configure the serial port for SCADAPack 535E to be as below : 

Port 0 Function : DNP3

Port 0 Mode : USB

Port 1 Function : DNP3

Port 1 Mode : Hayes Modem        (Siemens 3G modem)

Port 2 Function : PLC Devices

Port 2 Mode : RS232 (RTS On)      (Tait Analog Radio)

Port 3 Function : PLC Devices

Port 3 Mode : RS232 (RTS On)        (Tait Analog Radio)

However, we notice port 3 and port 4 only have selection for RS232 and RS485 2w. There's no selection available for RS232(RTS On) as this radio devices required such selection in order to work. Hence, I would like to seek for advise for any work around for such configuration as it was important to have all 3 modem and radio to be available in order for the entire network to work.

The fall side was the customer does not allow us to change the RTU model. I welcome any suggestion or recommendation. 

Thanks in advance any expert that willing to help out this issue. 

Thanks and regards.

[Joel_Weder]

As the RTU doesn't provide "RTS On" in port 3 or 4, the simplest way to do this is via a serial cable modification. Just tie RTS and CTS together at the radio end of the cable. The radio will presumably be setting its own CTS (clear to send) output pin true (high, +v) so that will loop right back in to set the RTS input. 

If for some reason the radio's CTS pin is not asserted (unlikely as it seems to be so insistent that its RTS line be asserted) another option, though more difficult, would be to apply a positive voltage to the radio's RTS pin from an external source (in the range of +3 to +15 volts), most simply from the radio's power supply. 

[BevanWeiss]

Only the two Tait radios will require RTS.

The Siemens 3G modem will not require this, and could use no flow control.

So you should be able to just change your configuration to have Port 1 / Port 2 as the Tait radios, and Port 3 as the 3G modem.

If the Tait radios are 'modern' it should even be possible to configure them without requiring RTS.  Generally only legacy (non-digital) radios really require RTS.  The rest just packetise up the data sent and dispatch it (without actually opening a dedicated 'line' between the two ends).