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6,001 | One book credits TI engineers Gary Boone and Michael Cochran with the successful creation of the first microcontroller in 1971. The result of their work was the TMS 1000, which became commercially available in 1974. It combined read-only memory, read/write memory, processor and clock on one chip and was targeted at emb... |
6,002 | During the early-to-mid-1970s, Japanese electronics manufacturers began producing microcontrollers for automobiles, including 4-bit MCUs for in-car entertainment, automatic wipers, electronic locks, and dashboard, and 8-bit MCUs for engine control. |
6,003 | Partly in response to the existence of the single-chip TMS 1000, Intel developed a computer system on a chip optimized for control applications, the Intel 8048, with commercial parts first shipping in 1977. It combined RAM and ROM on the same chip with a microprocessor. Among numerous applications, this chip would even... |
6,004 | Most microcontrollers at this time had concurrent variants. One had EPROM program memory, with a transparent quartz window in the lid of the package to allow it to be erased by exposure to ultraviolet light. These erasable chips were often used for prototyping. The other variant was either a mask-programmed ROM or a PR... |
6,005 | In 1993, the introduction of EEPROM memory allowed microcontrollers to be electrically erased quickly without an expensive package as required for EPROM, allowing both rapid prototyping, and in-system programming. The same year, Atmel introduced the first microcontroller using Flash memory, a special type of EEPROM. ... |
6,006 | Nowadays microcontrollers are cheap and readily available for hobbyists, with large online communities around certain processors. |
6,007 | In 2002, about 55% of all CPUs sold in the world were 8-bit microcontrollers and microprocessors. |
6,008 | Over two billion 8-bit microcontrollers were sold in 1997, and according to Semico, over four billion 8-bit microcontrollers were sold in 2006. More recently, Semico has claimed the MCU market grew 36.5% in 2010 and 12% in 2011. |
6,009 | A typical home in a developed country is likely to have only four general-purpose microprocessors but around three dozen microcontrollers. A typical mid-range automobile has about 30 microcontrollers. They can also be found in many electrical devices such as washing machines, microwave ovens, and telephones. |
6,010 | Cost to manufacture can be under US$0.10 per unit. |
6,011 | Cost has plummeted over time, with the cheapest 8-bit microcontrollers being available for under US$0.03 in 2018, and some 32-bit microcontrollers around US$1 for similar quantities. |
6,012 | In 2012, following a global crisis—a worst ever annual sales decline and recovery and average sales price year-over-year plunging 17%—the biggest reduction since the 1980s—the average price for a microcontroller was US$0.88 . |
6,013 | In 2012, worldwide sales of 8-bit microcontrollers were around US$4 billion, while 4-bit microcontrollers also saw significant sales. |
6,014 | In 2015, 8-bit microcontrollers could be bought for US$0.311 , 16-bit for US$0.385 , and 32-bit for US$0.378 . |
6,015 | In 2018, 8-bit microcontrollers could be bought for US$0.03, 16-bit for US$0.393 , and 32-bit for US$0.503 . |
6,016 | In 2018, the low-priced microcontrollers above from 2015 were all more expensive at: the 8-bit microcontroller could be bought for US$0.319 or 2.6% higher, the 16-bit one for US$0.464 or 21% higher, and the 32-bit one for US$0.503 or 33% higher. |
6,017 | On 21 June 2018, the "world's smallest computer" was announced by the University of Michigan. The device is a "0.04 mm3 16 nW wireless and batteryless sensor system with integrated Cortex-M0+ processor and optical communication for cellular temperature measurement." It "measures just 0.3 mm to a side—dwarfed by a grain... |
6,018 | A microcontroller can be considered a self-contained system with a processor, memory and peripherals and can be used as an embedded system. The majority of microcontrollers in use today are embedded in other machinery, such as automobiles, telephones, appliances, and peripherals for computer systems. |
6,019 | While some embedded systems are very sophisticated, many have minimal requirements for memory and program length, with no operating system, and low software complexity. Typical input and output devices include switches, relays, solenoids, LED's, small or custom liquid-crystal displays, radio frequency devices, and sens... |
6,020 | Microcontrollers must provide real-time response to events in the embedded system they are controlling. When certain events occur, an interrupt system can signal the processor to suspend processing the current instruction sequence and to begin an interrupt service routine which will perform any processing required ba... |
6,021 | Typically microcontroller programs must fit in the available on-chip memory, since it would be costly to provide a system with external, expandable memory. Compilers and assemblers are used to convert both high-level and assembly language code into a compact machine code for storage in the microcontroller's memory. Dep... |
6,022 | Manufacturers have often produced special versions of their microcontrollers in order to help the hardware and software development of the target system. Originally these included EPROM versions that have a "window" on the top of the device through which program memory can be erased by ultraviolet light, ready for repr... |
6,023 | Other versions may be available where the ROM is accessed as an external device rather than as internal memory, however these are becoming rare due to the widespread availability of cheap microcontroller programmers. |
6,024 | The use of field-programmable devices on a micro controller may allow field update of the firmware or permit late factory revisions to products that have been assembled but not yet shipped. Programmable memory also reduces the lead time required for deployment of a new product. |
6,025 | Where hundreds of thousands of identical devices are required, using parts programmed at the time of manufacture can be economical. These "mask-programmed" parts have the program laid down in the same way as the logic of the chip, at the same time. |
6,026 | A customized microcontroller incorporates a block of digital logic that can be personalized for additional processing capability, peripherals and interfaces that are adapted to the requirements of the application. One example is the AT91CAP from Atmel. |
6,027 | Microcontrollers usually contain from several to dozens of general purpose input/output pins . GPIO pins are software configurable to either an input or an output state. When GPIO pins are configured to an input state, they are often used to read sensors or external signals. Configured to the output state, GPIO pins ca... |
6,028 | Many embedded systems need to read sensors that produce analog signals. This is the purpose of the analog-to-digital converter . Since processors are built to interpret and process digital data, i.e. 1s and 0s, they are not able to do anything with the analog signals that may be sent to it by a device. So the analog-to... |
6,029 | In addition to the converters, many embedded microprocessors include a variety of timers as well. One of the most common types of timers is the programmable interval timer . A PIT may either count down from some value to zero, or up to the capacity of the count register, overflowing to zero. Once it reaches zero, it se... |
6,030 | A dedicated pulse-width modulation block makes it possible for the CPU to control power converters, resistive loads, motors, etc., without using many CPU resources in tight timer loops. |
6,031 | A universal asynchronous receiver/transmitter block makes it possible to receive and transmit data over a serial line with very little load on the CPU. Dedicated on-chip hardware also often includes capabilities to communicate with other devices in digital formats such as Inter-Integrated Circuit , Serial Peripheral ... |
6,032 | Microcontrollers may not implement an external address or data bus as they integrate RAM and non-volatile memory on the same chip as the CPU. Using fewer pins, the chip can be placed in a much smaller, cheaper package. |
6,033 | Integrating the memory and other peripherals on a single chip and testing them as a unit increases the cost of that chip, but often results in decreased net cost of the embedded system as a whole. Even if the cost of a CPU that has integrated peripherals is slightly more than the cost of a CPU and external peripherals,... |
6,034 | A microcontroller is a single integrated circuit, commonly with the following features: |
6,035 | This integration drastically reduces the number of chips and the amount of wiring and circuit board space that would be needed to produce equivalent systems using separate chips. Furthermore, on low pin count devices in particular, each pin may interface to several internal peripherals, with the pin function selected b... |
6,036 | Microcontrollers have proved to be highly popular in embedded systems since their introduction in the 1970s. |
6,037 | Some microcontrollers use a Harvard architecture: separate memory buses for instructions and data, allowing accesses to take place concurrently. Where a Harvard architecture is used, instruction words for the processor may be a different bit size than the length of internal memory and registers; for example: 12-bit ins... |
6,038 | The decision of which peripheral to integrate is often difficult. The microcontroller vendors often trade operating frequencies and system design flexibility against time-to-market requirements from their customers and overall lower system cost. Manufacturers have to balance the need to minimize the chip size against a... |
6,039 | Microcontroller architectures vary widely. Some designs include general-purpose microprocessor cores, with one or more ROM, RAM, or I/O functions integrated onto the package. Other designs are purpose-built for control applications. A microcontroller instruction set usually has many instructions intended for bit manipu... |
6,040 | Microcontrollers historically have not had math coprocessors, so floating-point arithmetic has been performed by software. However, some recent designs do include FPUs and DSP-optimized features. An example would be Microchip's PIC32 MIPS-based line. |
6,041 | Microcontrollers were originally programmed only in assembly language, but various high-level programming languages, such as C, Python and JavaScript, are now also in common use to target microcontrollers and embedded systems. Compilers for general purpose languages will typically have some restrictions as well as enha... |
6,042 | Microcontrollers with specialty hardware may require their own non-standard dialects of C, such as SDCC for the 8051, which prevent using standard tools even for code unrelated to hardware features. Interpreters may also contain nonstandard features, such as MicroPython, although a fork, CircuitPython, has looked to m... |
6,043 | Interpreter firmware is also available for some microcontrollers. For example, BASIC on the early microcontroller Intel 8052; BASIC and FORTH on the Zilog Z8 as well as some modern devices. Typically these interpreters support interactive programming. |
6,044 | Simulators are available for some microcontrollers. These allow a developer to analyze what the behavior of the microcontroller and their program should be if they were using the actual part. A simulator will show the internal processor state and also that of the outputs, as well as allowing input signals to be generat... |
6,045 | Recent microcontrollers are often integrated with on-chip debug circuitry that when accessed by an in-circuit emulator via JTAG, allow debugging of the firmware with a debugger. A real-time ICE may allow viewing and/or manipulating of internal states while running. A tracing ICE can record executed program and MCU sta... |
6,046 | As of 2008, there are several dozen microcontroller architectures and vendors including: |
6,047 | Many others exist, some of which are used in very narrow range of applications or are more like applications processors than microcontrollers. The microcontroller market is extremely fragmented, with numerous vendors, technologies, and markets. Note that many vendors sell or have sold multiple architectures. |
6,048 | In contrast to general-purpose computers, microcontrollers used in embedded systems often seek to optimize interrupt latency over instruction throughput. Issues include both reducing the latency, and making it be more predictable . |
6,049 | When an electronic device causes an interrupt, during the context switch the intermediate results have to be saved before the software responsible for handling the interrupt can run. They must also be restored after that interrupt handler is finished. If there are more processor registers, this saving and restoring pr... |
6,050 | Other factors affecting interrupt latency include: |
6,051 | Lower end microcontrollers tend to support fewer interrupt latency controls than higher end ones. |
6,052 | Two different kinds of memory are commonly used with microcontrollers, a non-volatile memory for storing firmware and a read-write memory for temporary data. |
6,053 | From the earliest microcontrollers to today, six-transistor SRAM is almost always used as the read/write working memory, with a few more transistors per bit used in the register file. |
6,054 | In addition to the SRAM, some microcontrollers also have internal EEPROM and/or NVRAM for data storage; and ones that do not have any , or where the internal memory is insufficient, are often connected to an external EEPROM or flash memory chip. |
6,055 | A few microcontrollers beginning in 2003 have "self-programmable" flash memory. |
6,056 | The earliest microcontrollers used mask ROM to store firmware. Later microcontrollers had EPROM memory, which used a translucent window to allow erasure via UV light, while production versions had no such window, being OTP . Firmware updates were equivalent to replacing the microcontroller itself, thus many products w... |
6,057 | Motorola MC68HC805 was the first microcontroller to use EEPROM to store the firmware. EEPROM microcontrollers became more popular in 1993 when Microchip introduced PIC16C84 and Atmel introduced an 8051-core microcontroller that was first one to use NOR Flash memory to store the firmware. Today's microcontrollers almost... |
6,058 | A system on a chip or system-on-chip is an integrated circuit that integrates most or all components of a computer or other electronic system. These components almost always include on-chip central processing unit , memory interfaces, input/output devices and interfaces, and secondary storage interfaces, often alongsi... |
6,059 | Higher-performance SoCs are often paired with dedicated and physically separate memory and secondary storage chips, that may be layered on top of the SoC in what's known as a package on package configuration, or be placed close to the SoC. Additionally, SoCs may use separate wireless modems. |
6,060 | An SoC integrates a microcontroller, microprocessor or perhaps several processor cores with peripherals like a GPU, Wi-Fi and cellular network radio modems, and/or one or more coprocessors. Similar to how a microcontroller integrates a microprocessor with peripheral circuits and memory, an SoC can be seen as integratin... |
6,061 | Compared to a multi-chip architecture, an SoC with equivalent functionality will have reduced power consumption as well as a smaller semiconductor die area. This comes at the cost of reduced replaceability of components. By definition, SoC designs are fully or nearly fully integrated across different component modules.... |
6,062 | SoCs are very common in the mobile computing and edge computing markets. |
6,063 | In general, there are three distinguishable types of SoCs: |
6,064 | SoCs can be applied to any computing task. However, they are typically used in mobile computing such as tablets, smartphones, smartwatches and netbooks as well as embedded systems and in applications where previously microcontrollers would be used. |
6,065 | Where previously only microcontrollers could be used, SoCs are rising to prominence in the embedded systems market. Tighter system integration offers better reliability and mean time between failure, and SoCs offer more advanced functionality and computing power than microcontrollers. Applications include AI accelerati... |
6,066 | Mobile computing based SoCs always bundle processors, memories, on-chip caches, wireless networking capabilities and often digital camera hardware and firmware. With increasing memory sizes, high end SoCs will often have no memory and flash storage and instead, the memory and flash memory will be placed right next to, ... |
6,067 | In 1992, Acorn Computers produced the A3010, A3020 and A4000 range of personal computers with the ARM250 SoC. It combined the original Acorn ARM2 processor with a memory controller , video controller , and I/O controller . In previous Acorn ARM-powered computers, these were four discrete chips. The ARM7500 chip was the... |
6,068 | Tablet and laptop manufacturers have learned lessons from embedded systems and smartphone markets about reduced power consumption, better performance and reliability from tighter integration of hardware and firmware modules, and LTE and other wireless network communications integrated on chip . |
6,069 | An SoC consists of hardware functional units, including microprocessors that run software code, as well as a communications subsystem to connect, control, direct and interface between these functional modules. |
6,070 | An SoC must have at least one processor core, but typically an SoC has more than one core. Processor cores can be a microcontroller, microprocessor , digital signal processor or application-specific instruction set processor core. ASIPs have instruction sets that are customized for an application domain and designed ... |
6,071 | SoCs must have semiconductor memory blocks to perform their computation, as do microcontrollers and other embedded systems. Depending on the application, SoC memory may form a memory hierarchy and cache hierarchy. In the mobile computing market, this is common, but in many low-power embedded microcontrollers, this is n... |
6,072 | SoCs include external interfaces, typically for communication protocols. These are often based upon industry standards such as USB, FireWire, Ethernet, USART, SPI, HDMI, I²C, CSI, etc. These interfaces will differ according to the intended application. Wireless networking protocols such as Wi-Fi, Bluetooth, 6LoWPAN and... |
6,073 | When needed, SoCs include analog interfaces including analog-to-digital and digital-to-analog converters, often for signal processing. These may be able to interface with different types of sensors or actuators, including smart transducers. They may interface with application-specific modules or shields. Or they may be... |
6,074 | Digital signal processor cores are often included on SoCs. They perform signal processing operations in SoCs for sensors, actuators, data collection, data analysis and multimedia processing. DSP cores typically feature very long instruction word and single instruction, multiple data instruction set architectures, an... |
6,075 | Typical DSP instructions include multiply-accumulate, Fast Fourier transform, fused multiply-add, and convolutions. |
6,076 | As with other computer systems, SoCs require timing sources to generate clock signals, control execution of SoC functions and provide time context to signal processing applications of the SoC, if needed. Popular time sources are crystal oscillators and phase-locked loops. |
6,077 | SoC peripherals including counter-timers, real-time timers and power-on reset generators. SoCs also include voltage regulators and power management circuits. |
6,078 | SoCs comprise many execution units. These units must often send data and instructions back and forth. Because of this, all but the most trivial SoCs require communications subsystems. Originally, as with other microcomputer technologies, data bus architectures were used, but recently designs based on sparse intercommun... |
6,079 | Historically, a shared global computer bus typically connected the different components, also called "blocks" of the SoC. A very common bus for SoC communications is ARM's royalty-free Advanced Microcontroller Bus Architecture standard. |
6,080 | Direct memory access controllers route data directly between external interfaces and SoC memory, bypassing the CPU or control unit, thereby increasing the data throughput of the SoC. This is similar to some device drivers of peripherals on component-based multi-chip module PC architectures. |
6,081 | Wire delay is not scalable due to continued miniaturization, system performance does not scale with the number of cores attached, the SoC's operating frequency must decrease with each additional core attached for power to be sustainable, and long wires consume large amounts of electrical power. These challenges are pro... |
6,082 | In the late 2010s, a trend of SoCs implementing communications subsystems in terms of a network-like topology instead of bus-based protocols has emerged. A trend towards more processor cores on SoCs has caused on-chip communication efficiency to become one of the key factors in determining the overall system performanc... |
6,083 | Networks-on-chip have advantages including destination- and application-specific routing, greater power efficiency and reduced possibility of bus contention. Network-on-chip architectures take inspiration from communication protocols like TCP and the Internet protocol suite for on-chip communication, although they typi... |
6,084 | Many SoC researchers consider NoC architectures to be the future of SoC design because they have been shown to efficiently meet power and throughput needs of SoC designs. Current NoC architectures are two-dimensional. 2D IC design has limited floorplanning choices as the number of cores in SoCs increase, so as three-di... |
6,085 | A system on a chip consists of both the hardware, described in § Structure, and the software controlling the microcontroller, microprocessor or digital signal processor cores, peripherals and interfaces. The design flow for an SoC aims to develop this hardware and software at the same time, also known as architectural ... |
6,086 | Most SoCs are developed from pre-qualified hardware component IP core specifications for the hardware elements and execution units, collectively "blocks", described above, together with software device drivers that may control their operation. Of particular importance are the protocol stacks that drive industry-standar... |
6,087 | SoCs components are also often designed in high-level programming languages such as C++, MATLAB or SystemC and converted to RTL designs through high-level synthesis tools such as C to HDL or flow to HDL. HLS products called "algorithmic synthesis" allow designers to use C++ to model and synthesize system, circuit, sof... |
6,088 | Once the architecture of the SoC has been defined, any new hardware elements are written in an abstract hardware description language termed register transfer level which defines the circuit behavior, or synthesized into RTL from a high level language through high-level synthesis. These elements are connected together... |
6,089 | Chips are verified for validation correctness before being sent to a semiconductor foundry. This process is called functional verification and it accounts for a significant portion of the time and energy expended in the chip design life cycle, often quoted as 70%. With the growing complexity of chips, hardware verifica... |
6,090 | Traditionally, engineers have employed simulation acceleration, emulation or prototyping on reprogrammable hardware to verify and debug hardware and software for SoC designs prior to the finalization of the design, known as tape-out. Field-programmable gate arrays are favored for prototyping SoCs because FPGA prototyp... |
6,091 | With high capacity and fast compilation time, simulation acceleration and emulation are powerful technologies that provide wide visibility into systems. Both technologies, however, operate slowly, on the order of MHz, which may be significantly slower – up to 100 times slower – than the SoC's operating frequency. Accel... |
6,092 | FPGA prototypes, in contrast, use FPGAs directly to enable engineers to validate and test at, or close to, a system's full operating frequency with real-world stimuli. Tools such as Certus are used to insert probes in the FPGA RTL that make signals available for observation. This is used to debug hardware, firmware and... |
6,093 | In parallel, the hardware elements are grouped and passed through a process of logic synthesis, during which performance constraints, such as operational frequency and expected signal delays, are applied. This generates an output known as a netlist describing the design as a physical circuit and its interconnections. T... |
6,094 | SoCs must optimize power use, area on die, communication, positioning for locality between modular units and other factors. Optimization is necessarily a design goal of SoCs. If optimization was not necessary, the engineers would use a multi-chip module architecture without accounting for the area use, power consumptio... |
6,095 | Common optimization targets for SoC designs follow, with explanations of each. In general, optimizing any of these quantities may be a hard combinatorial optimization problem, and can indeed be NP-hard fairly easily. Therefore, sophisticated optimization algorithms are often required and it may be practical to use appr... |
6,096 | For broader coverage of trade-offs and requirements analysis, see requirements engineering. |
6,097 | SoCs are optimized to minimize the electrical power used to perform the SoC's functions. Most SoCs must use low power. SoC systems often require long battery life , can potentially spend months or years without a power source while needing to maintain autonomous function, and often are limited in power use by a high nu... |
6,098 | SoCs are optimized to maximize power efficiency in performance per watt: maximize the performance of the SoC given a budget of power usage. Many applications such as edge computing, distributed processing and ambient intelligence require a certain level of computational performance, but power is limited in most SoC env... |
6,099 | SoC designs are optimized to minimize waste heat output on the chip. As with other integrated circuits, heat generated due to high power density are the bottleneck to further miniaturization of components.: 1 The power densities of high speed integrated circuits, particularly microprocessors and including SoCs, have b... |
6,100 | In particular, most SoCs are in a small physical area or volume and therefore the effects of waste heat are compounded because there is little room for it to diffuse out of the system. Because of high transistor counts on modern devices, oftentimes a layout of sufficient throughput and high transistor density is physic... |
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