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hi
I am using four TMS320F28335 on my board, I am able to debug and program 3 of them, I am using Blackhawk USB2000 and code composer version 4. As I was trying to troubleshoot the problem, why I am not able to program one processor. I observe following things:
1. Reset Pin XRS (pin 80) is pulled low for 500 micro second. This happens at a frequency of 217 Hz always, when the external oscillator is connected.
2. when external oscillator is not connected the reset pin does not go low.
3. The external clock is stable and provide 30MHz signal.
4. We removed external watchdog, still the above mention condition is occurring.
5. Our dual voltage regulator also provides external reset, both reset pin of the regulator were lifted from board, still the above mention condition is occurring.
if I am not mistaking the only thing that can pull the reset pin low is the chips internal watch dog. Is it possible that the chip is code protected and might have a code which does not disable the internal watch dog. please provide the possible cause for above said problem.
Looking at the reset pin XRS signal on the scope, the falling edge is rapid and is being actively sharply pulled down (ie transistor action). All external reset devices (watchdog and reset pins of voltage regulator were removed). This appears to be TMS internally generated reset with WDRST buffer pulling pin 80 XRS pin LOW at 217Hz or 4.6msec repetitively (ie digitally timed precision). We have external pull up resistors on the XRS reset line to preclude noise induced spurious external reset.
What we are hoping to learn are the conditions which lead WDRST buffer pulling pin 80 XRS pin LOW and why it involves the 4.6msec interval, assuming our understanding of the WDRST buffer being connected to the pin 80 XRS pin is correct.
thank you
Amol
