JTAG UART hangs on disconnection of terminal

While I'm not that familiar with the JTAG UART this sounds like the typical behaviour of FIFO with overrun protection - i.e. of there are as an example three Tx-Buffers, the UART generates (when disconnected) an error to the code with all three Tx Buffers filled up. Thus you either need to change your code to check for messages being transmitted (i.e. Tx Buffers are cleared) or (if this is supported) you need have some routine to deal with an Error flag (Tx Buffer overflow)... Some UART provide a mode to just overwrite "not sent" messages cyclic (don't know if the JTAG UART supports this) - this might be the option you are looking for...