Program Counter and ROM space in 8051 and register bank
1. Unit-III-A
8051 Microcontroller
Functional block diagram and pin diagram of 8051,
Power supply, clock and reset circuit,
Program Counter and ROM space in 8051,
Program and Data Memory organization,
addressing modes. Instruction Set of 8051: data
transfer, arithmetic and logical, program branching
instructions, single bit manipulation, shift and
Boolean variable manipulation, Interrupt of 8051.
2. • The 8051 microcontroller has 4 kilobytes (4 KB) of
internal ROM (Read-Only Memory). The ROM is non-
volatile, meaning its contents cannot be changed.
• What is ROM?
• ROM is a type of memory that stores programs as
read-only data.
• ROM is used to store executable functions and data
that is unlikely to change.
3. • Other 8051 memory
• The 8051 also has 128 bytes of internal RAM (Random Access
Memory). RAM is a general-purpose memory that stores user data in a
program.
• The 8051 has a serial port and 32 I/O pins.
• Modern 8051 variants
• Most modern 8051 microcontrollers, like the 8052 series, have 8 KB of
internal ROM.
• They also have the option to reprogram the memory.
• Most modern variants of the 8051 microcontroller have 256 bytes of
RAM.
• External memory
• The 8051 can also access external memory using a set of instructions.
6. Types of addressing modes:
• Direct addressing mode: The address field points
directly to the memory location where data is stored
• Indirect addressing mode: The address field points to
a register and then to the intended memory location
• Register addressing mode: The source and
destination are registers
• Immediate addressing mode: The programmer can
directly specify a constant or immediate value
