Question

Explain memory register map of 8051 Micro-controller with diagram.

Answer 1

The 8051 addresses has two separate memory spaces:
i. Program memory space.
ii. Data memory space.

(b) The memory map for 8051 is shown in the following figure.
(c) The program memory space is Read- only memory (ROM) space.
(d) This memory space is used for storing programs and variable data.
(e) It is possible to read program instructions form this space, but the processor cannot write data into this memory.
(f) All instruction fetches are taken from program memory space.
(g) The data memory space is read/write memory space.
(h) The processor can read data read data from this memory space and can write data to this memory space.
(i) It cannot execute instructions from this memory space. The 8051 internal RAM is in this memory space.
(j) The 128 bytes of internal RAM provide general read/write data storage. Some part of this is memory space.
(k) The 8051 has 22 special function registers which are not part of 128 bytes of RAM. They occupy memory space from 80H to F8H. These registers are used for their intended purpose.
(l) The 4K byte program memory can be expanded by an additional 60k bytes, making it 64K bytes program memory. The data memory can also be expanded to 64K bytes.
(m) The 8051 can also be operated with common memory. In this case, 8051 only has 64K bytes of total external memory. In this configuration, 8051 can input block of data through its serial communications port load that data in memory and then execute that data as a program. This is called downloaded program. It is a very common technique used to change the program operating in a remote microprocessor- based controller.