Please can somone tell me how I test my firewire?

Hi there

My focusrite safire pro 14 stopped getting a connection to the firewire. It is still being pwered by the firewire though. I have updated both Mac OS to Yosemite and compatible focusrite software and still wont work. I have also changed the lead just in case it was that. I want to find out if the error is with the pro 14 or my mac. For that I thought I would test the firewire but dont know how. I have no other firewire connected hardware to test with though.

Thanks in advance for your help.

Sarah