Hello Group,
I'm the software guy working on a new board and the hardware guy is telling me that this is a software problem. I'll help him in his quest.
We have built a few prototype boards (10) and six of them cannot communicate with the BDM. The other four do. I've check that there is a clock and that there are no shorts. The strange thing is that the reset seems to be asserted low and stays there on some boards.
1. Why would the CPU reset pin be asserted low and stay there?
2. The BDM claims that there is no clock or it is not connected to the CPU. What are some of the items I should be looking for to figure out why the BDM does not communicate?
Thanks for your help.
Hi,
Thanks for the help.
Here is the scenario:
* Clock - 10MHz looks as if it is going to the CPU and good.
* Reset controller looks like it is working. Disconnect the CPU (lift pin) reset from the reset controller and you see the reset pulse at power-up from the reset controller. However, looking at the raw (disconnected) RESET pin on the CPU, it shows low. When the reset controller is connected to the CPU RESET pin, you can see that it is trying to reset the CPU. You can see very little change in the “low” state.
* Power pins looks good.
My only guess it that some of the CPU pins are not connected correctly or there may be missing connections. A little frustrating, but I am looking at the HW datasheet.
TIA
Hello All,
Thanks for your help. I was able to show the HW guy that he had the wrong voltage. He was trying to feed the CPU 3.5V where it should have been 5V. I think that this was the root of the problem. The datasheet showed a 4.5V minimum.
Again thanks for the help.