SLAU320AJ July 2010 – May 2021
The core JTAG logic integrated into devices that support 2-wire mode is identical to 4-wire-only devices. The fundamental difference is that 2-wire devices implement additional logic that is used to convert the 2-wire communication into the standard 4-wire communication internally. In this way, the existing JTAG emulation methodology of the MSP430 can be fully used.
The 2-wire interface is made up of the SBWTCK (Spy-Bi-Wire test clock) and SBWTDIO (Spy-Bi-Wire test data input/output) pins. The SBWTCK signal is the clock signal and is a dedicated pin. In normal operation, this pin is internally pulled to ground. The SBWTDIO signal represents the data and is a bidirectional connection. To reduce the overhead of the 2-wire interface, the SBWTDIO line is shared with the RST/NMI pin of the device.
Section 2.6 describes the MSP430 devices and their respective JTAG interface implementation.