Misterious problem leading microcontroller to not work!

[AceOfHearts]

For the past 6 months I have a circuit on a breadboard consisting of a microcontroller and LCD was working...recently my code would download, but the microcontroller would not execute the program (since yesterday)...its like it is frozen and none of the pins do what its meant to do....some pins are outputting rubbish but periodic signals that dont mean anything...I dont know whats wrong, I replaced the microcontroller with brand new ones, and still all of them are giving the same problem....I pressed reset, turn the power on and off and what not.

I have checked my oscillator circuit, replaced the crystal...probed with logic probes and osciolloscopes here and there to no avail.

Usually, a problem can be solved after time...but this one, spending hours and still cant figure out whats going on here. Could it be something so trivial and so under my noise that Im overlooking it?

Any ideas? The microcontroller is an 8051 if anyone is interested.

 

[AceOfHearts]

Got the problem identified I think.

 

[3v0]

And the problem is ?

 

[AceOfHearts]

Basically, I had two LCDs connected to the same microcontroller. The problem started when I removed one of the two to solder it on somewhere else. The microcontroller would appear not to work because in my code, I first write something to the LCD which I had removed and without that LCD in place, the code got stuck there at the begin, probably in an infinite loop or something perhaps checking a busy flag of the LCD.

Turned out there was nothing wrong with the microcontrollers or the breadboard.