When do I use xdata?

Question

I am new at embedded system programming. I am working on a device that uses an 8051 chipset. I have noticed in the sample programs that when defining variables, sometimes they u

Answer 1

How and when to use xData memory area depends on the system architecture. Some systems may have RAM at this address while others could have ROM or Flash. In either case, access will be slower than accessing internal RAM, ROM or Flash.

Generally speaking, large items, constant items and lesser used items should go into xData. There are no standard rules as to what goes in xData, as it depends on the architecture.