Why does the MCU use the C language? The superiority of the C language

Single chip microcomputer STM32L151CCU6

1206RGB (single)

SHTF27111500%C

The transition from C to microcontroller units (MCUs), particularly the widely used 8051 architecture, started in the mid to late 1980s. However, porting C to 8051 was not straightforward due to several technical challenges. For example:

• The 8051 uses a Harvard architecture, separating program and data memory spaces, which makes it difficult for traditional C compilers designed for von Neumann architectures.

• The on-chip memory is limited, and there's often a need to expand it externally, which complicates memory management.

• Special Function Registers (SFRs) are not mapped to standard I/O address spaces, making direct hardware access more complex.

• The 8051 family has hundreds of variants, each with unique features. C must handle all these differences without exceptions.

Despite these challenges, companies like Keil, Franklin, IAR, and others worked tirelessly to adapt C for MCUs. By the 1990s, C had matured into a powerful tool for MCU development. The early concerns—such as slow execution speed and large code size—have been significantly reduced. Today, C code on 8051 is about 1.2 to 1.5 times the size of assembly code, and can fit within 4K bytes of RAM. With the help of simulators and manual optimization, performance can be optimized to meet even the most demanding requirements.

In terms of development speed, code quality, structure, and reliability, C clearly outperforms assembly language. It’s time for MCU developers to embrace C as their primary programming language.

Here are some key advantages of using C for single-chip microcontrollers:

• You don’t need to know the instruction set to write effective programs.

• You can develop professional-level software without deep knowledge of the specific MCU hardware.

• C helps manage data efficiently, making the best use of limited RAM.

• Programs written in C are more robust, with better handling of data integrity and protection against unexpected corruption.

• C offers advanced data types like arrays, structures, pointers, and unions, giving you greater flexibility and power.

• It provides memory qualifiers such as auto, static, and const, along with specialized memory types like data, idata, pdata, xdata, and code for 8051. These help optimize memory usage automatically.

• Compilation modes like small, compact, and large allow you to tailor the code size to your MCU’s memory constraints.

• Interrupt handling, including saving and restoring context, is managed by the compiler, reducing the burden on the developer.

• A rich library of standard functions is available for immediate use.

• Header files support macro definitions, complex data types, and function prototypes, improving code portability and supporting product line development.

• C enforces strict syntax rules, helping catch errors early and making debugging faster.

• It supports various utility services, such as automatic initialization of on-chip resources or integration with real-time operating systems, simplifying user development and improving system stability.