SLAU320AJ July 2010 – May 2021
This macro loads a JTAG instruction into the JTAG instruction register (IR) of the target device. In the MSP430, this register is eight bits wide with the least significant bit (LSB) shifted in first. The data output from TDO during a write to the JTAG instruction register contains the version identifier of the JTAG interface (or JTAG ID) that is implemented on the target device. The JTAG ID is shifted out with MSB first.
Regardless of the 8-bit instruction sent out on TDI, the return value on TDO is always the JTAG ID. Each instruction bit is captured from TDI by the target MSP430 on the rising edge of TCK. TCLK should not change state while this macro is executed (TCLK = TDI while the TAP controller is in the Run-Test/Idle state). Figure 2-3 shows how to load the ADDR_16BIT instruction into the JTAG IR. See Section 2.2.4 for a complete list of the JTAG interface communication instructions that are used to access the flash memory module of the target device.