A
system on a chip or
system on chip (
SoC or
SOC) is an
integrated circuitAn integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
(
IC) that integrates all components of a
computerA computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
or other
electronicElectronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
systemSystem is a set of interacting or interdependent components forming an integrated whole....
into a single chip. It may contain
digitalA digital signal is a physical signal that is a representation of a sequence of discrete values , for example of an arbitrary bit stream, or of a digitized analog signal...
,
analogAn analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
, mixed-signal, and often radio-frequency functions—all on a single chip substrate. A typical application is in the area of embedded systems.
The contrast with a
microcontrollerA microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
is one of degree. Microcontrollers typically have under 100 kB of RAM (often just a few kilobytes) and often really
are single-chip-systems, whereas the term SoC is typically used with more powerful processors, capable of running software such as the desktop versions of
WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
and
LinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, which need external memory chips (flash, RAM) to be useful, and which are used with various external peripherals. In short, for larger systems
system on a chip is hyperbole, indicating technical direction more than reality: increasing chip integration to reduce manufacturing costs and to enable smaller systems. Many interesting systems are too complex to fit on just one chip built with a process optimized for just one of the system's tasks.
When it is not feasible to construct an SoC for a particular application, an alternative is a
system in packageA system-in-a-package or system in package , also known as a Chip Stack MCM, is a number of integrated circuits enclosed in a single package or module. The SiP performs all or most of the functions of an electronic system, and are typically used inside a mobile phone, digital music player, etc...
(SiP) comprising a number of chips in a single
packageA chip carrier, also known as a chip container or chip package, is a container for a transistor or an integrated circuit. The carrier usually provides metal leads, or "pins", which are sturdy enough to electrically and mechanically connect the fragile chip to a circuit board. This connection may be...
. In large volumes, SoC is believed to be more cost-effective than SiP since it increases the yield of the fabrication and because its packaging is simpler.
Another option, as seen for example in higher end cell phones and on the
Beagle BoardThe BeagleBoard is a low-power, low-cost open source hardware single-board computer produced by Texas Instruments in association with Digi-Key. The BeagleBoard was also designed with open source software development in mind, and as a way of demonstrating the Texas Instrument's OMAP3530...
, is
package on packagePackage on package is an integrated circuit packaging method to combine vertically discrete logic and memory ball grid array packages. Two or more packages are installed atop each other, i.e. stacked, with a standard interface to route signals between them...
stacking during board assembly. The SoC chip includes processors and numerous digital peripherals, and comes in a ball grid package with lower and upper connections. The lower balls connect to the board and various peripherals, with the upper balls in a ring holding the memory buses used to access NAND flash and DDR2 RAM. Memory packages could come from multiple vendors.
Structure
A typical SoC consists of:
- A microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
, microprocessorA microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
or DSPA digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...
core(s). Some SoCs—called multiprocessor system on chip (MPSoCThe multiprocessor System-on-Chip is a system-on-a-chip which uses multiple processors , usually targeted for embedded applications...
)—include more than one processor core.
- Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....
blocks including a selection of ROMRead-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
, RAM, EEPROMEEPROM stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., calibration...
and flash memoryFlash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data...
.
- Timing sources including oscillators and phase-locked loop
A phase-locked loop or phase lock loop is a control system that generates an output signal whose phase is related to the phase of an input "reference" signal. It is an electronic circuit consisting of a variable frequency oscillator and a phase detector...
s.
- Peripherals including counter
In digital logic and computing, a counter is a device which stores the number of times a particular event or process has occurred, often in relationship to a clock signal.- Electronic counters :...
-timers, real-time timerA timer is a specialized type of clock. A timer can be used to control the sequence of an event or process. Whereas a stopwatch counts upwards from zero for measuring elapsed time, a timer counts down from a specified time interval, like an hourglass.Timers can be mechanical, electromechanical,...
s and power-on resetA power-on reset generator is a microcontroller or microprocessor peripheral that generates a reset signal when power is applied to the device...
generators.
- External interface
An electrical connector is an electro-mechanical device for joining electrical circuits as an interface using a mechanical assembly. The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or...
s including industry standards such as USBUSB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
, FireWire, EthernetEthernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
, USART, SPIThe Serial Peripheral Interface Bus or SPI bus is a synchronous serial data link standard named by Motorola that operates in full duplex mode. Devices communicate in master/slave mode where the master device initiates the data frame. Multiple slave devices are allowed with individual slave select ...
.
- Analog
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
interfaces including ADCs and DACs.
- Voltage regulator
A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. A voltage regulator may be a simple "feed-forward" design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components...
s and power managementPower management is a feature of some electrical appliances, especially copiers, computers and computer peripherals such as monitors and printers, that turns off the power or switches the system to a low-power state when inactive. In computing this is known as PC power management and is built...
circuits.
These blocks are connected by either a proprietary or industry-standard
busIn computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same...
such as the
AMBAThe Advanced Microcontroller Bus Architecture is used as the on-chip bus in system-on-a-chip designs. Since its inception, the scope of AMBA has gone far beyond microcontroller devices, and is now widely used on a range of ASIC and SoC parts including applications processors used in modern...
bus from
ARM HoldingsARM Holdings plc is a British multinational semiconductor and software company headquartered in Cambridge. Its largest business is in processors, although it also designs, licenses and sells software development tools under the RealView and KEIL brands, systems and platforms, system-on-a-chip...
.
DMADirect memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....
controllers route data directly between external
interfaceAn electrical connector is an electro-mechanical device for joining electrical circuits as an interface using a mechanical assembly. The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or...
s and memory, bypassing the processor core and thereby increasing the data throughput of the SoC.
Design flow
An SoC consists of both the
hardwarePersonal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...
described above, and the
softwareComputer software, or just software, is a collection of computer programs and related data that provide the instructions for telling a computer what to do and how to do it....
that controls the
microcontrollerA microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
,
microprocessorA microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
or
DSPDigital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
cores, peripherals and interfaces. The
design flowDesign flows are the explicit combination of electronic design automation tools to accomplish the design of an integrated circuit. Moore's law has driven the entire IC implementation RTL to GDSII design flows from one which uses primarily...
for an SoC aims to develop this hardware and software in parallel.
Most SoCs are developed from pre-qualified
hardware blocksIn electronic design a semiconductor intellectual property core, IP core, or IP block is a reusable unit of logic, cell, or chip layout design that is the intellectual property of one party. IP cores may be licensed to another party or can be owned and used by a single party alone...
for the hardware elements described above, together with the
software driversIn computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....
that control their operation. Of particular importance are the
protocol stackThe protocol stack is an implementation of a computer networking protocol suite. The terms are often used interchangeably. Strictly speaking, the suite is the definition of the protocols, and the stack is the software implementation of them....
s that drive industry-standard interfaces like
USBUSB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
. The hardware blocks are put together using CAD tools; the
software modulesModular programming is a software design technique that increases the extent to which software is composed of separate, interchangeable components called modules by breaking down program functions into modules, each of which accomplishes one function and contains everything necessary to accomplish...
are integrated using a
software-development environmentAn integrated development environment is a software application that provides comprehensive facilities to computer programmers for software development...
.
Chips are verified for logical correctness before being sent to foundry. This process is called
functional verificationFunctional verification, in electronic design automation, is the task of verifying that the logic design conforms to specification. In everyday terms, functional verification attempts to answer the question "Does this proposed design do what is intended?" This is a complex task, and takes the...
and it accounts for a significant portion of the time and energy expended in the chip design life cycle (although the often quoted figure of 70% is probably an exaggeration). With the growing complexity of chips,
hardware verification languageA Hardware Verification Language, or HVL, is a programming language used to verify the designs of electronic circuits written in a hardware description language. HVLs typically include features of a high-level programming language like C++ or Java as well as features for easy bit-level...
s like
SystemVerilogIn the semiconductor and electronic design industry, SystemVerilog is a combined Hardware Description Language and Hardware Verification Language based on extensions to Verilog.-History:...
,
SystemCSystemC is a set of C++ classes and macros which provide an event-driven simulation kernel in C++ . These facilities enable a designer to simulate concurrent processes, each described using plain C++ syntax...
,
ee is a hardware verification language which is tailored to implementing highly flexible and reusable verification testbenches.- History :...
, and
OpenVeraOpenVera is a dead Hardware Verification Language developed, and managed by Synopsys.OpenVera is an interoperable, open hardware verification language for testbench creation. The OpenVera language was used as the basis for the advanced verification features in the IEEE Std...
are being used.
BugsA software bug is the common term used to describe an error, flaw, mistake, failure, or fault in a computer program or system that produces an incorrect or unexpected result, or causes it to behave in unintended ways. Most bugs arise from mistakes and errors made by people in either a program's...
found in the verification stage are reported to the designer.
Often, one step in the verification flow is
emulationIn computing, an emulator is hardware or software or both that duplicates the functions of a first computer system in a different second computer system, so that the behavior of the second system closely resembles the behavior of the first system...
: The hardware is mapped onto an emulation platform based on a
field-programmable gate arrayA field-programmable gate array is an integrated circuit designed to be configured by the customer or designer after manufacturing—hence "field-programmable"...
(FPGA) that mimics the behavior of the SoC, and the software modules are loaded into the
memoryRandom access memory is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time. Strictly speaking, modern types of DRAM are therefore not random access, as data is read in...
of the emulation platform. Once programmed, the emulation platform enables the hardware and software of the SoC to be tested and
debuggedDebugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware, thus making it behave as expected. Debugging tends to be harder when various subsystems are tightly coupled, as changes in one may cause bugs to emerge...
at close to its full operational speed. Emulation is generally preceded by extensive software simulation. In fact, sometimes the FPGAs are used primarily to speed up some parts of the simulation work.
After emulation the hardware of the SoC follows the
place-and-routePlace and route is a stage in the design of printed circuit boards, integrated circuits, and field-programmable gate arrays. As implied by the name, it is composed of two steps, placement and routing. The first step, placement, involves deciding where to place all electronic components, circuitry,...
phase of the design of an integrated circuit before it is fabricated.
Fabrication
SoCs can be fabricated by several
technologiesTechnology is the making, usage, and knowledge of tools, machines, techniques, crafts, systems or methods of organization in order to solve a problem or perform a specific function. It can also refer to the collection of such tools, machinery, and procedures. The word technology comes ;...
, including:
- Full custom
Full-custom design is a methodology for designing integrated circuits by specifying the layout of each individual transistor and the interconnections between them...
- Standard cell
In semiconductor design, standard cell methodology is a method of designing application-specific integrated circuits with mostly digital-logic features. Standard cell methodology is an example of design abstraction, whereby a low-level very-large-scale integration layout is encapsulated into an...
- FPGA
A field-programmable gate array is an integrated circuit designed to be configured by the customer or designer after manufacturing—hence "field-programmable"...
SoC designs usually consume less power and have a lower cost and higher reliability than the multi-chip systems that they replace. And with fewer packages in the system, assembly costs are reduced as well.
However, like most VLSI designs, the total cost is higher for one large chip than for the same functionality distributed over several smaller chips, because of lower yields and higher
NRENon-recurring engineering refers to the one-time cost to research, develop, design and test a new product. When budgeting for a project, NRE must be considered to analyze if a new product will be profitable...
costs.
Books
See also
- List of system-on-a-chip suppliers
- PSoC
PSoC is a family of integrated circuits made by Cypress Semiconductor. These chips include a CPU and mixed-signal arrays of configurable integrated analog and digital peripherals.- History :...
- ASIC
An application-specific integrated circuit is an integrated circuit customized for a particular use, rather than intended for general-purpose use. For example, a chip designed solely to run a cell phone is an ASIC...
- Microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
- Electronic design automation
Electronic design automation is a category of software tools for designing electronic systems such as printed circuit boards and integrated circuits...
- Post silicon validation
Post-silicon validation and debug is the last step in the development of a semiconductor integrated circuit. During the pre-silicon process, engineers test devices in a virtual environment with sophisticated simulation, emulation, and formal verification tools...
- System in package
A system-in-a-package or system in package , also known as a Chip Stack MCM, is a number of integrated circuits enclosed in a single package or module. The SiP performs all or most of the functions of an electronic system, and are typically used inside a mobile phone, digital music player, etc...
- Single-board computer
A single-board computer is a complete computer built on a single circuit board, with microprocessor, memory, input/output and other features required of a functional computer. Unlike a typical personal computer, an SBC may not include slots into which accessory cards may be plugged...
- Network On Chip
Network-on-Chip or Network-on-a-Chip is an approach to designing the communication subsystem between IP cores in a System-on-a-Chip . NoCs can span synchronous and asynchronous clock domains or use unclocked asynchronous logic...
External links
- SOCC Annual IEEE
The Institute of Electrical and Electronics Engineers is a non-profit professional association headquartered in New York City that is dedicated to advancing technological innovation and excellence...
International SOC Conference