MSP430FE42XA Datasheet, PDF (40/44 Pages) Texas Instruments – MIXED SIGNAL MICROCONTROLLER

MSP430FE42xA
MIXED SIGNAL MICROCONTROLLER
SLAS588 -- FEBRUARY 2008
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, I_TF, 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 only flows 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
I_TF
I_TDI/TCLK
Figure 18. Fuse Check Mode Current, MSP430FE42xA
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