An Introduction to the Advanced Microprocessors

A microcontroller is a complete microprocessor system integrated into a single chip, incorporating a microprocessor along with limited amounts of RAM, ROM, and I/O components. This integration significantly reduces the cost of building simple products that utilize microprocessor capabilities for control functions. Unlike a standalone microprocessor, a microcontroller includes essential components such as parallel I/O ports, timers, a clock, and often a serial port, making it more complex. Essentially, it functions as a microcomputer, specifically designed for control tasks. Microcontrollers evolved after microprocessors and are widely used in various applications due to their compact and cost-effective nature. 

Advantages of Microcontroller 

1. Microcontrollers can be used for specific, dedicated functions in various applications. 
2. They can act as independent controllers in machines, managing tasks on their own. 
3. Microcontrollers include all essential components of a computer (CPU, RAM, ROM) on a single chip, allowing them to function as standalone microcomputers. 
4. They reduce system costs compared to microprocessor-based systems, making them ideal for low-cost products like toys

Microcontrollers are versatile devices used in both simple tasks like timing and bit manipulation, and complex high-speed data processing. They are essential in low-cost products like electronic toys, microwave ovens, and VCRs, as well as in more advanced applications such as machine tools, chemical processing, and medical instruments. In personal computers, microcontrollers streamline keyboard functions by replacing traditional circuits. Their broad application across household appliances, industrial machinery, and computing devices highlights their critical role in modern electronics.

The 8088 and 8086 processors define the base programming model for the X86 family. Newer X86 processors, like the 386 and 486, offer greater computing power with faster speeds, 32-bit registers, and advanced addressing. The programming model consists of three register groups: eight general-purpose registers (AX, BX, CX, DX, SI, DI, BP, SP), which become 32-bit (EAX, EBX, etc.) in newer processors; segment registers (CS, SS, DS, ES, FS, GS) for managing memory operations; and the instruction pointer (IP) and flag register, which are either 16-bit or 32-bit, depending on the processor. These registers handle data storage, memory operations, and instruction execution. 

Programming Model Diagram

 Flag Register in X 86 Family

The first 5 bits are identical to 8085 flag. The bits 6 - 11 were introduced with 8088/8086. The bits 12- 14 were introduced with 286. 16th and 17th bits were introduced with 386 and 18th was introduced with 486 

Additional Features 

X86 processors enhance speed through instruction prefetching and data caching. They cache instructions in an internal memory or prefetch queue, making them instantly available for processing, thus reducing fetch cycle delays. Additionally, frequently used data is stored in an on-chip cache, minimizing the need for external memory access and further accelerating processing time.

In the last fifty years, semiconductor technology has rapidly evolved. Starting with transistors and integrated circuits (ICs) in the 1950s, advancements led to small scale integration (SSI), medium scale integration (MSI), and large-scale integration (LSI). Today, we have very-large scale integration (VLSI) and super large-scale integration (SLSI). Microprocessors, from the Intel 4004 to 32-bit CPUs, have revolutionized computing and control applications. Microprocessor are classified into four generations which are discussed in subtopics below 

First generation 

The first microprocessor, the Intel 4004, was introduced in 1971 by scientist Fagin for use in calculators and was not suitable for general computing. In 1972, Intel released the 8008, the first 8-bit microprocessor, featuring 45 instructions and using LSI technology. Ex: INTEL 4040, Toshiba's T 3472 

Second generation 

In 1976, the 8085, an 8-bit microprocessor, was introduced. Microprocessor development aimed to integrate a complete microcomputer system, including CPU, ROM, RAM, clock, and I/O ports, into a single package. Ex: Intel 8048, motorala MC 6801 etc. 

Third generation 

Another key direction in microprocessor evolution has been creating processors that function like minicomputers, handling bytes, character strings, and instruction cycles of 1 microsecond. In 1978, Intel introduced the high-performance 16-bit microprocessor, the 8086 (APX 86), developed by Stephen Mors and Druce Revenal. Ex.: INTEL 8086, 8088, zylog z8000, M 6800 etc. 

Fourth generation 

In 1981, Intel introduced the 32-bit 80386 microprocessor, capable of addressing 4 gigabytes of physical memory. Examples include M68020, HP32, and iAPX432. Recently, Intel released Pentium I, II, III, IV, Core 2 Duo, and Xeon, the most advanced microprocessors