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MSP430G2121: Can I double use the JTAG and SPI

Part Number: MSP430G2121
Other Parts Discussed in Thread: MSP-EXP430G2, MSP-FET

Can I double use the JTAG and SPI.  I am looking at the MSP430G2121 for a design, it has TCK,TMS,TDI,TDO on the same pins as SCLK,SDO,SDI.

Does the part know to mux functionality between being a jtag for debugging and being a SPI for the firmware app?

  • a0321875 said:
    Can I double use the JTAG and SPI.

    Not at the same time. When you want to use SPI on particular pins, you shall disable debug function on them. You can use Spy-Bi-Wire for debugging instead, then you don't have such dilemma.  Spy-Bi-Wire TEST and ~RST pins does not conflict with any peripheral.

  • Can I use my standard MSP-FETFLASH emulator to debug with the SPY-bi-wire interface or is there a differnent JTAG tool? Is there an interfacing appnote or details (pull ups?) on the spy-bi-wire ?
  • Hi all,

    I also would recommend to use Spy-Bi-Wire because it uses only the dedicated RST and TEST pins so it will not conflict with a peripheral. You can program the device using the full 4-wire JTAG, but while in debug mode with the tool connected you would be unable to use the SPI muxed on these pins. With the tool disconnected it would not be a problem - basically, when the tool performs the debug entry sequence it will select these pins for the debug function rather than the normal SPI function and ignore your pin muxing settings. So stand-alone it is not a problem, but it would make it hard to debug your application because you couldn't use SPI and JTAG at the same time. (Note also that if you use one of the Launchpads like MSP-EXP430G2, that is already using Spy-Bi-Wire for this exact reason of limited pins on the device).

    So as mentioned I would use Spy-Bi-Wire instead.

    : Are you referring to the TI MSP-FET tool This supports both JTAG and Spy-Bi-Wire - you simply have to connect the pins on the MSP430 to the MSP-FET in a different configuration. This is explained in the MSP430 Hardware Tool's User's guide figure 2-2 Signal Connections for 2-Wire JTAG Communication (Spy-Bi-Wire) for G2xx. If you follow these connections (pay close attention to R's and C's specified in the diagram), you should be able to program the device using Spy-Bi-Wire. In CCS and IAR, the selection for using Spy-Bi-Wire is automatic - you don't need to change anything in your project settings. For software tools like the Elprotronic FET-Pro430 Lite software that works with MSP-FET, you need to specify to use Spy-Bi-Wire under Setup > Connection / Device Reset. Does this answer your question?