Microcontroller, and modern ARM Cortex cores., Slides of Microprocessors

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MICROCONTROLLER

Microcontroller

• A semiconductor IC (integrated circuit) chip consists of multiple functional blocks such as CPU, ROM, RAM, Timer, Counter & interrupts etc.
• A small computer with all peripheral inside a single package.

Basis of Bus-Width

• Bus - refers to the parallel lines of connection between various components of the microcontroller. It transmits the instructions & data between the CPU, memory and input/output ports.
• Three types of buses inside a microcontroller; data bus, address bus, control bus.
• Bus width - refers to the number of parallel lines or wires or connections present in the said bus. Increasing the bus-width of a microcontroller increases its precision and its overall performance of the microcontroller.

Basis of Bus-Width

• On the basis of bus width, the microcontrollers are divided into 8-Bit, 16-bit & 32-bit microcontrollers. Bus Layout in Microcontroller

16 - bit Microcontroller

• The bus width is 16 bit (2 byte) wide. It can transfer and process a data of 16 bits in a single cycle.
• Its 16-bit ALU is more efficient in performance comparing to 8-bit microcontroller. And its 16-bit timer provides a wide range of 0x0000 (0) to 0xFFFF (65535) which provides the best accuracy per cost for any application or projects that require Timer functions.
• Common examples of a 16-bit microcontrollers are 8051XA, PIC2x, Intel 8096 and Motorola MC68HC12 families.

32 - bit Microcontroller

• A 32-bit microcontroller has a bus width of 32 bits or 4 bytes long. The performance & accuracy of such microcontroller is higher than 16-bit microcontroller but they are also expensive and consume a lot of power.
• Its higher processing speed makes it the best candidate for performing a complex tasks such as audio and video signal processing, image processing, etc. It can also support multiple peripheral required in any embedded system projects or applications such as Ethernet, Universal Serial Bus (USB), Universal Asynchronous Receiver-Transmitter devices (UARTS), and a Controller Area Network (CAN) bus.
• The common 32-bit microcontrollers are Intel/Atmel 251 family, PIC3x.

Embedded Memory Microcontroller

• Has all the essential memory blocks or modules embedded inside a single package. Some of these functional blocks are program and data memory, timers & counter, interrupts etc.
• These memory blocks are fixed and not expendables but a microcontroller having the feature of supporting external ROMs can extend its storage memory. These are compact in design. Embedded Memory Microcontroller

External Memory Microcontroller

• Does not have one of the essential memory blocks inside its chip and it needs to be connected externally to function properly. The use of external modules increases the size of the overall device. External Memory Microcontroller

Basis of Instruction Set Architecture

• A complex instruction set is made from combination of multiple instructions i.e. to execute a complex instruction; the microcontroller needs to execute various simple instructions.
• Some of the complex function in a microcontroller is moving data to and from multiple registers, copying strings of data, square root, log, sine etc.
• Types: CISC (Complex Instruction Set Computer) and RISC (Reduced Instruction Set Computers)

CISC (Complex Instruction Set

Computer)

• Designed to execute a single complex command. It can execute multiple instructions or steps using a single instruction.
• The advantage of CISC microcontroller is its small-sized program. But due to the large size of its instruction set with many addressing modes, it takes a multiple machine cycle to execute and causes longer time to perform.
• Another problem is the parallel execution of an instruction which is not possible in CISC.

Basis of Microcontroller Architecture

• Microcontroller architecture is a set of rules that defines the functionality & implementation of a microcontroller.
• The program memory (ROM) is used for storing and accessing the code or the instruction. While the data memory (RAM) is used for storing & accessing the data used by these instructions.
• Types: Harvard Architecture Microcontroller and Von Neumann (or Princeton) Architecture Microcontroller

Harvard Architecture Microcontroller

• Has physically separate memory storage for program code (instructions) and the data, known as the program memory and the data memory respectively
• Have separate bus lines and can be accessed both at the same time
• Can complete instruction in one machine cycle

Von Neumann (or Princeton)

Architecture Microcontroller

• Suggests to use a single memory for both the program and data storage.
• This concept was proposed by a mathematician Von Neumann in 1945 and it is the most used architecture in all computers, desktop & laptops to date.
• There is only one bus required for accessing data and fetching instructions. Thus, both operations cannot be done at the same time and they must be scheduled.

Von Neumann (or Princeton)

Architecture Microcontroller

• Takes two machine cycles to complete an instruction. Since it uses a single bus system, its design is simple and production is very low compared to Harvard architecture. Von Neumann Architecture based Microcontroller