Wong Siu Hang wrote:
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"...but before I even switch on the toggle switch, the LED has already turned on. Can anyone tell me what are the possible reasons for this?"

Is it possible that your microcontroller is executing preemptive code that anticipates what you are about to do? ;)

Your code is written such that the toggle switches and LED's should be on a memory-mapped bus. Is this true?

If the LED's and switches are connected directly to the port pins, which I suspect is the case, move data to and from the port SFR that the respective hardware is connected to. MOVX is used to access addresses on an external memory-mapped bus.

- Lee