SLAS616 datasheet(41/52 Pages) TI2

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MSP430FE42x2

MIXED SIGNAL MICROCONTROLLER

SLAS616 − JULY 2008

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

JTAG fuse check mode

MSP430 devices that have the fuse on the TDI/TCLK terminal have a fuse-check mode that tests the continuity

of the fuse the first time the JTAG port is accessed after a power-on reset (POR). When activated, a fuse check

current, ITF, of 1.8 mA at 3 V can flow from the TDI/TCLK pin to ground if the fuse is not burned. Care must be

taken to avoid accidentally activating the fuse-check mode and increasing overall system power consumption.

Activation of the fuse check mode occurs with the first negative edge on the TMS pin after power up or if the

TMS is being held low during power up. The second positive edge on the TMS pin deactivates the fuse check

mode. After deactivation, the fuse check mode remains inactive until another POR occurs. After each POR, the

fuse-check mode has the potential to be activated.

The fuse-check current flows only when the fuse-check mode is active, and the TMS pin is in a low state (see

Figure 18). Therefore, the additional current flow can be prevented by holding the TMS pin high (default

condition).

The JTAG pins are terminated internally and, therefore, do not require external termination.

Time TMS Goes Low After POR

TMS

ITF

ITDI/TCLK

Figure 18. Fuse Check Mode Current, MSP430FE42x2

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