I am trying to make a temperature scanner with ADuC845(8051 core). sir I have checked the following voltage levels at following pins:
1) AVdd=5.0V 2) AGND=0.0V 3) DVdd=4.57V wrt DGND 4) PSEN= 4.31V 5) ALE= 4.55V 6) XTAL1 and XTAL2= 4.55V
the current drawn by the board when LCD IS NOT CONNECTED is 54mA and the current drawn by the board when LCD is removed is 8.5mA
in both the above cases the current drawn is seemingly higher than max ratings. what is the probable fault and the solution???
What do you mean by "max ratings"? Remember that the max current consumption mentioned for the processor is for just the processor. External hardware, pull-ups/pull-downs, MAX232 transceivers etc will add to the consumption.
A LCD consumes very little power, so either you are including the backlighting. One thing to verify is of course that you never have two outputs fighting for the state of a signal. When signals are DC-clockable, it is often a good idea to add huge delays between each step of the code (potentially requiring a key press to step one step) to allow you to use a multimeter to verify the DC levels of all signals for each step of the code. This can of course be made faster with access to a digital oscilloscope with a suitable number of channels. This may catch situations where you are requesting a read from the display, but the processor is forcing the data signals low (or, if the processor supports push-pull, the processor is forcing the data signals high).
It would have been better to have continued in the original thread: http://www.keil.com/forum/docs/thread16128.asp#msg82076