Datasheet

Time TMS Goes Low After POR

TMS

TEST

MSP430F22x2

MSP430F22x4

SLAS504G –JULY 2006–REVISED AUGUST 2012

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JTAG Fuse Check Mode

MSP430 devices that have the fuse on the TEST 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, I

, of 1 mA at 3 V, 2.5 mA at 5 V can flow from the TEST 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.

When the TEST pin is again taken low after a test or programming session, the fuse check mode and sense

currents are terminated.

Activation of the fuse check mode occurs with the first negative edge on the TMS pin after power up or if 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 28). Therefore, the additional current flow can be prevented by holding the TMS pin high (default

condition).

Figure 28. Fuse Check Mode Current

NOTE

The CODE and RAM data protection is ensured if the JTAG fuse is blown and the 256-bit

bootloader access key is used. Also, see the Bootstrap Loader section for more

information.