Data Transfer 80C51

Internal RAM
Table 3 shows the menu of instructions that are available for moving data around within the internal memory spaces, and the addressing modes that can be used with each one. With a 12MHz clock, all of these instructions execute in either 1 or 2ms. The MOV [dest], [src] instruction allows data to be transferred between any two internal RAM or SFR locations without going through the Accumulator.

Instruction Set of 80C51

Arithmetic Instructions
The menu of arithmetic instructions is listed in Table 1.4.1 The table indicates the addressing modes that can be used with each instruction to access the operand.
For example, the ADD A, instruction can be written as:

Addressing modes in the 80C51

The addressing modes in the 80C51 instruction set are as follows:
An "addressing mode" refers to how you are addressing a given memory location. In summary, the addressing modes are as follows, with an example of each:

Special Function Register Microcontroller

A Map of the on-chip memory area called the Special Function Register (SFR) space is shown in Figure 1.2.1. Note that in the SFRs not all of the addresses are occupied. Unoccupied addresses are not implemented on the chip. Read accesses to these addresses will in general return random data, and write accesses will have no effect.

Microcontroller MCS-51 Architecture

Memory Organization

All 80C51 devices have separate address spaces for program and data memory, as shown in Figures 1.1.1 and 1.1.2. The logical separation of program and data memory allows the data memory to be accessed by 8-bit addresses, which can be quickly stored and