On the UCD3138, JTAG comms are disabled by default by the ROM code that executes on device startup. This video outlines the steps required to enable comms on the UCD3138 when the part is in ROM mode. Please note that this step applies only to the UCD3138 and is NOT required for the following devices:- UCD3138A- UCD3138064- UCD3138064A- UCD3138A64- UCD3138128- UCD3138128A