DSP: What’s all the excitement about?

DSP or Digital Signal Processing by itself is quite mind boggling in terms of

technology and range of applications. Devices that will deliver the power of

today's laptop in a device the size of a wristwatch may not be very far off, if

increasing chip performance is anything to go by. In the near future, there

could be a single chip composed of dozens of digital signal processor (DSP)

chips, each with 500 million transistors integrated into it. This level of DSP

performance, combined with reduced power consumption and space requirements, is

vital for applications such as DSP-based residential gateways, Internet TV,

wearable health monitoring devices, autonomous home robots and real-time

videophones

DSP explained



To start at the very beginning, what is DSP? As the name itself indicates,
deals with the various techniques employed in processing digital signals. In

most cases, the initial signal is in the form of an analog electrical voltage or

current which is converted into digital (i.e. numerical) form before DSP

techniques can be applied. An analog signal can be digitized using an

analog-to-digital converter or ADC. This generates a digital output in the form

of a binary number whose value represents the analog input to the device. In an

increasingly digital world, analog signals need to be first converted to digital

signals to take advantage of the many benefits that digital signals provide.

Digital signals allow for easy manipulation and elaborate modification of audio

and video signals, which provides for greater flexibility. These capabilities

are exactly what DSPs exploit. Once a signal has been reduced to numbers, its

components can be isolated, analyzed and rearranged more easily than in analog

form.

The term DSP can be used for the techniques used to process digital signals

or the digital signal processor that is used to perform the number crunching

operations involved in digital signal processing. The processor has specialized

set of instructions, architecture, bus structure and addressing modes that set

it apart from its more well known counterpart, the general purpose

microprocessor. Another key difference between the two is that DSPs have a

dedicated multiplier accumulator function called MAC. The MAC takes care of the

heavy number crunching operations and the memory architecture in turn is

optimized to support this. Another basic difference is that apart from the

general addressing modes, DSPs have bit reverse addressing which is specifically

targeted for Fast Fourier Transforms. Fast Fourier Transforms allow the

frequency spectrum of a signal to be computed rapidly.

When we talk of speed in chips, the first thing that comes to mind is clock

speed but in the case of DSP, the term clock speed can be misleading. Processing

capabilities can be better gauged when you take into account that they are

capable of performing about 10 billion operations per second. This need for

speed is powered by the requirements to provide real-time performance: that is,

the ability to process a signal "live" as it is sampled and then

output the processed signal.

DSP chips are capable of carrying out millions of floating point operations

per second and for most manufacturers it’s a continuous race to manufacture

faster and more powerful ones.