We have been using the ADuC847 for several years. Lately we are getting communication error when trying to reset the controller. The response from the controller indicates its a baud rate error. We tried to replace the crystal or controller and that sometimes work and most of the times do not. We are getting about 10% failures on the production line. We would like to get to the root cause for this problem and would appreciate any help to solve this problem. We are using the ADuC847 52-pin package. In addition some controller would work initially at the manufactures and then later would start getting the same bad characters indicating communication error and does not allow to load any programs.
One way to isolate the problem is to check if all power supplies are at the correct levels. Then please check the crystal, if the crystal is bad - the chip won't function as expected and will not reply…
You mentioned that you have been using the ADuC847 ago, is it failing on a new application? New circuit design? or is there any changes to the user code?
It is the same design and the problem is directly related to communication and downloading code. When resetting the board rather than obtaining response back indicating the controller version as ADuC 847 or so I get back bad characters indicating communication errors. In production say we manufacture 200 boards, out of the 200 we would get 30 boards with this problem or failure. User code has nothing to do with it and its not a new application or new circuit design. Could this be related to manufacturing issue or maybe moister affecting the controller or the crystal?
One way to isolate the problem is to check if all power supplies are at the correct levels. Then please check the crystal, if the crystal is bad - the chip won't function as expected and will not reply an ID during download mode.