title: What's inside a debugger box and how does it work exactly
body: <p>I'm working with an iSystem debugger box used for debugging automotive embedded systems. </p>
  
  <p>I can't help but wonder what is inside such boxes and how they work exactly.</p>
  
  <p>I understand only that there is a USB interface on one end and a JTAG interface on the other. There will be electronics to convert the USB signals to TTL I guess, but after this I'm not sure.</p>
  
  <p>Is the box just responsible for setting breakpoints in our code in real time over the JTAG interface (commanded by us) and relaying information about the state of the MCU back to us over USB? What would be in there exactly that makes it so complex and expensive? </p>