Magellan software opens port 1 only when Magellan software is used and shuts down the port when the program closes. Because I assume you are loading Primo from the SD card, the Magellan software does not fully load and port 1 never opens so TMC in Primo will not work.
After a lot of searching I have found a roundabout way to get TMC working with Primo on my Magellan Roadmate 5175T-LM. It wasn’t an easy task, there are quite a few steps that need to be followed, so proceed at your own risk, I will not be held responsible if your unit stops working.
Please note, this is a very basic overview of what I did to get TMC working with Primo on my Magellan not a step by step guide. As always, BEFORE YOU DO ANYTHING, backup (copy) all of the files on your GPS unit to your computers hard drive before making any changes.
I used Miopocket Mini using “Method #1: SD Card Installation”, but be aware; you will need to change some lines in its installation script to get TMC to work. You will also need to add TMC files for your country to Primo (which can be found elsewhere on this site) so it can decode the signals. You will have to add some lines to Primos sys.txt (source, port, baud, ect.). You may also need the proper tmc .dll files. I strongly recommend using the diMkaWA_P174 skin as it has the most flexibility to tune in stations with TMC signals.
TMC in the United States and Canada is used only in major metropolitan areas and some of those areas only transmit TMC signals during weekday rush hours while others transmit 24/7. You can go to [Only registered and activated users can see links. ] to see if your area is covered.