The porting of C to the MCU (commonly known as microcontroller) 8051 began in the late 1980s. Objectively speaking, there are many challenges in porting C to the 8051 MCU, such as:
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The non-Von Neumann architecture of the 8051 (with separate program and data memory spaces), along with the additional bit-addressable memory space on the chip;
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The limited on-chip data and program memory space, coupled with the possibility of expanding them off-chip;
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The integration of peripheral devices on-chip being register-based (i.e., SFR), rather than using the conventional I/O address space;
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The large number of derivative types of the 8051 chip (over a hundred), and the necessity for C language to operate on each of their hardware resources without exception.
These challenges were not present in C languages based on MPUs in the past. Thanks to the tireless efforts of companies like Keil/Franklin, Archmeades, IAR, and BSO/Tasking, the C language for MCUs began to mature in the 1990s, becoming a specialized high-level language for MCUs. The long-standing issue of “high-level languages generating excessively long code and running too slowly, thus being unsuitable for microcontrollers” has been largely overcome. Currently, the code length of C on the 8051 has been reduced to 1.2 to 1.5 times that of assembly language. Beyond 4K bytes, the advantages of C language become even more pronounced. As for execution speed, with the help of good simulators, identifying critical code and further optimizing it manually can easily achieve satisfactory results. When it comes to development speed, software quality, structural rigor, and program robustness, the perfection of C language is incomparable to assembly language programming. Today, it is indeed time for MCU developers to wield the powerful tool of C language.
Below, we will discuss the advantages of using C language for microcontrollers, specifically the 8051:
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One can write perfect microcontroller programs without understanding the instruction set of the microcontroller;
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It is possible to write professionally-level programs that conform to hardware realities without needing to understand the specific hardware of the microcontroller;
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Data from different functions can overlap, effectively utilizing the limited RAM space on-chip;
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Programs exhibit robustness: data corruption is a significant factor leading to abnormal program execution. C language provides many professional treatments for data, avoiding asynchronous corruption during execution;
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C language offers complex data types (arrays, structures, unions, enumerations, pointers, etc.), greatly enhancing program processing capabilities and flexibility;
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It provides storage types such as auto, static, const, and specialized storage types for the 8051 microcontroller like data, idata, pdata, xdata, code, automatically allocating addresses for variables;
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It offers compilation modes such as small, compact, and large to accommodate the size of on-chip memory;
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The protection and restoration of the context in interrupt service routines, as well as the filling of the interrupt vector table, are directly related to the microcontroller and are handled by the C compiler;
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It provides a library of commonly used standard functions for users to utilize directly;
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Macros defined in header files, along with complex data types and function prototypes, facilitate program portability and support the development of serialized products for microcontrollers;
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There is strict syntax checking, resulting in fewer errors that can be quickly eliminated at a high-level language level;
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It conveniently accepts services from various utility programs: for instance, on-chip resource initialization can be automatically generated by dedicated utility programs; furthermore, real-time multitasking operating systems can schedule multiple tasks, simplifying user programming and enhancing operational safety, etc.
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