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MSP430G2201 blowing the fuse does not disable the SBW interface

Other Parts Discussed in Thread: MSP430G2201

When I applied 6.5V to pin 11 of the MSP430G2201 "Test" pin (TSSOP package) I expected to disable the Spy-bi-wire interface but I can download new code. I held the voltage to the pins for about 3 seconds. I took the board and applied the voltage from a bench power supply current limited to 500mA with the ground lead conneccted to pin 14 (Ground).

According to the datasheet once the fuse is blown the SBW is disabled.

Why can I still download code?

Since the flash is accessable is my code secure?

With the fuse blown can I still write to the flash?

Did I blow the fuse or do I need to apply a higher voltage?

  • The maximum Vpp is 7V (see the data-sheet). But apply Vpp to TEST pin is not sufficient to blow the JTAG fuse. You need to follow the procedure described on page 46 of SLAU320.pdf.

    1.4.1.1.2 Fuse-Programming Voltage Via TEST Pin
    The same method is used to program the fuse for the TEST pin MSP430 devices, with the exception that
    the fuse-blow voltage, VPP, is now applied to the TEST input pin.
    IR_SHIFT(“IR_PREPARE_BLOW”)
    MsDelay(1) : Delay for 1ms
    Connect VPP to TEST pin
    Wait until VPP input has settled (depends on VPP source)
    IR_SHIFT(“IR_EX_BLOW”)
    MsDelay(1) : Delay for 1ms
    Remove VPP from TEST pin
    Reset the JTAG state machine (ResetTAP)

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