System on Chip ( SoC )

System on Chip ( SoC )

Today's mobile phones have more processing power than typical desktop computers of the last millennium. Even the Portable Media Players (PMPs) have more sophisticated processors than the revolutionary Pentium processor launched 15 years back. On top of that, mobile phones, PMPs and other handheld devices are getting smaller and thinner with increasing battery life.

So, what makes these new generation handheld devices tick? Ticking at 200MHz or more, these devices are powered by a small silicon chip -the size of about 10mm x 10mm, which contains almost all components of a powerful computer including processor core, memory controller, interrupt controller, timer, multimedia co-processors or digital signal processor (DSP) etc. This silicon chip, along with the software running on it, is called a System-on-Chip or SoC.

We use a cutting-edge technology for development of electronics and devices based on Systems-on-Chip (SoC) from the leading semiconductor manufacturers such as Intel, Texas Instruments, Atmel, Sharp, and NetSilicon. This breakthrough technology allows creating competitive products with rich functionality while saving your time-to-market and expenses. Electronic device development with a new functional level based on MCU or DSP require significant amount of resources and a highly qualified team of hardware engineers, often resulting in failing to fit into project time frame.

The SoC has been talked about, marketed, and accepted in the new millennium, especially for embedded applications. More recently, with announcements of high-performance SoC designs such as the Cell chip, and use of these chips in consumer products including the Sony PlayStation 3 (PS3) and Microsoft® XBox, it has become clear that SoC designs will have broad impact. What is really exciting about SoC architecture is that supercomputing and embedded computing may become the cutting edge of computer architecture. For supercomputing this is nothing new, but embedded systems have often followed rather than led architecture.

What is a SoC?
System-on-chip is an integration of almost all components of a computer into a single integrated circuit (chip). The SoC consists of both the hardware (HW) components of the computer as well as the software (SW) that controls the microprocessor and peripherals.

SoCs include not only the brains (e.g. microprocessor) but also all required ancillary electronics, such as switches, comparators, resistors, capacitors, timing elements, and digital logic. While having the required interfaces (for example Ethernet, USB, LCD) onboard and almost the same functionality as a single board industrial computer (SBC), the embedded System-on-Chip (SoC) module provides additional advantages such as minimized footprint, operation in extended temperature range, minimized power consumption suitable for use in mobile environments. 
Structure of SoC

A typical SoC consists of:
§  One microcontroller, one microprocessor or DSP core(s). Some SOCs – called multiprocessor System-on-Chip (MPSoC) – include more than one processor core.
§  Memory blocks including a selection of ROM, RAM, EEPROM and Flash.
§  Timing sources including oscillators and phase-locked loops.
§  Peripherals including counter-timers, real-time timers and power-on reset generators.
§  External interfaces including industry standards such as USB, FireWire, Ethernet, USART, SPI.
§  Analog interfaces including ADCs and DACs.
§  Voltage regulators and power management circuits.

·    Processor such as ARM core.
·    System bus-connecting the processor to other components- e.g. AMBA Bus.
·    Memory-some types of ROM, EEPROM or Flash.
·    Timers-oscillators, PLLs, real time clocks etc.
·    LCD controllers or VGA Controller, with optional Touch Screen interface.
·    External Interfaces for USB, Firewire, etc. & for flash memory- Compact Flash, SD Card, Memory Stick etc.
·    Power management circuits, Interrupt Controller and Memory Interface.

·      The operating system - ranges from a simple RTOS like eCOS or uITRON to high level OS such as Windows CE or Embedded Linux.
·      The operating system layer, generally termed as the Board Support Package (BSP) abstracts the actual SoC HW.
·      Device drivers - which control the peripherals.
·      Middleware components - such as multimedia engines, protocol stacks etc.
·      Application software - the UI, the media players, phone applications, browsers etc.

Table 1: Components of SoC

These blocks are connected by either a proprietary or industry-standard bus such as the AMBA bus from ARM. DMA controllers route data directly between external interfaces and memory, by-passing the processor core and thereby increasing the data throughput of the SoC.

The generic SoC architecture consists of the processor, system bus, timers, memory, interrupt controller and power management circuits. The other peripherals such as LCD controllers, USB interface; Flash memory interfaces etc. are optional and depend on the target application of the SoC.
SoCs for multimedia platforms such as mobile phones or PMPs, require a large amount of audio and video processing. There are two schools of thoughts in the industry to achieve better multimedia experience for the user: Dedicated DSP and Dedicated multimedia blocks.

Some SoC designers use a dedicated DSP along with the main processor. The Audio and Video processing is shared between the main processor and the DSP. E.g. the main processor may be decoding audio, while the video is decoded on the DSP. This approach allows for more generic application of the SoC and also allows scalability in the future as new codecs are
released in the market. But this approach may increase the size of the chip and also increase the power utilization.
Other designers prefer using dedicated blocks for processing popular Audio and Video encoding formats. E.g. there can be dedicated hardware blocks for MP3 decoding, H.264 decoding, MPEG4 encoding etc. This approach may be more optimized in terms of size and power, but application and scalability may be limited.

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