ez430 - WDT problem?

Development Boards MicroMod
1

Hello out there,

a few weeks ago i bought an ez430 usb stick-debugger-emulator from ti. I did some silly things with the led and decided to solder an own target, equipped with a dip controller. I put the whole usb-stick into a small case. I put the target on a small board and connected it via short cable to the case. So far no probs.

Then I started the (IAR) debugger and did some (silly) led blinking - without any probs. I then equipped the target board with an own voltage source (using a lm317, adjusted to 3.60 V). I then observed a major problem. It seems to me, that the controller gets resetted after some amount of time - like a watchdog reset. In the code - of course - i put the (first) line - after main():

WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

I think this problem is no software problem - debugging runs!

The question - what else can cause a reset of the controller - what shall i measure first?

The difference, i found out between the debugger and my own target is, that the TST pin is high while debugging and low on my target - but should be no prob.

Any ideas?

2

I am not sure how are all your pieces connected together. But it sounds like both the USB tool and your LM317 are supplying power to the target. This is not a good idea.

If you read the TI documentation, you will see that on the tool side of ez430, Vcc is connected to one of the 4 pins that are connected to the target side. There is a 0R there. You should either remove (difficult to do) that resistor, or do not connect that pin to your target (easier to do). Either way, the target will be powered by the LM317 only, and not by the USB tool at the same time.

3

Ok. Fixed the problem.

It was an errorous voltage supply. Voltage sunk below 1 V for some amount of time and caused a brown-out reset of the controller.

Thanks.