In this protocol only two connections are used instead of the usual four pins for the general JTAG interface. The two connections are a bidirectional data output, and a clock. The clocking signal is split into a period of three clock pulses, for each clock pulse the TDI, TDO and TMS signals are passed on the micro controller via the bidirectional data output. 
- "MSP430™ Programming Via the JTAG Interface". Texas Instruments. 2010.