Data Transfer:

Moving

These instructions do accurately what you would think. They move data around among the various registers and memory.

Exchanging

It is a variation on the move instruction. Here data is exchanged among two places.

Memory and Addressing

There are many different types of memory in a microprocessor. One is Program memory. This is where the program is situated. Another is Data memory. It is where data that might be utilized by the program is located. The strange thing is that they both reside in the same memory space and can be changed by the program. That's right, in fact a program can alter itself if that was essential. Two terms are utilized when talking about memory. Reading (load) refers to getting a value from memory and writing (store) is putting a value into memory.

There are three buses connected with the memory subsystem. One is the address bus, the second is the data bus, and the third is the control bus. It's significant for you to know exactly how all this works, since these buses transport data and addresses everywhere. All three are associated to the memory subsystem. It is also good to know the function of each to better understand what's happening. In the 8085 CPU, the address bus is 16 bits broad. It acts to choose one of the unique 216 (64K) memory locations. The control bus finds out whether this shall be a read or a write. In the particular case of an instruction fetch, the control bus is set up for read operation. Data is written or read through the data bus, which is 8 bits wide. This is why all of the registers and memory are 8 bits wide, its the width of the data bus on the 8085 CPU. A bus is only a group of connections that all share a common function. Instead of speaking of each bit or connection in the address separately, for instance, all 16 are taken together and referred to simply as the address bus. The similar is true for the control and data buses.