How can the EM35x devices be debugged with IAR?
Debugging in IAR for the EM35x devices is almost completely handled in the standard manner. However, one interesting bit is that EM35x IAR projects default to debugging via a USB connection to the ISA3, so if you only have your ISA3 debugger hooked up via Ethernet, you need to go to Project >> Options >> Debugger >> JLink/JTrace >> Communications and change it from USB to TCP and enter the IP address of the ISA3 as per the adapter details in Ember Desktop (or your knowledge of the ISA3 settings).
A very important difference is that "Download and debug" does not work because IAR does not have a proper flashloader for our EM35x family. In this case you need to use em3xx_load/ commander or Ember Desktop GUI /Simplicity Studio GUI to download the image onto the chip and then use "Debug without Downloading" in IAR to start debugging.