Lecture Notes

1. MODULE IV
Digital signal processor: Digital signal processor and its design
issues, evolving architecture of DSP, next generation DSP.
Customizable processors: Customizable processors and processor
customization, A benefit analysis of processor customization, use of
microprocessor cores in SOC design, benefits of microprocessor
extensibility.

2. DSP And Its Impact On Technology
Book: Processor Design Systems On Chip
Computing For ASICs And FPGAs

3. Introduction

4. • DSP is a relatively new science. It has its roots in a
group of universities following the discovery (or
rediscovery) of the Fast Fourier Transform (FFT) in the
mid-1960s by Cooley and Tukey,
• The only computing resources available were
mainframe computers, it requires a significant number
of multiplications and additions.
•Because signal processing it was impossible to do any
of the research in real time.
The early beginning of DSP

5. An Algorithm For Machine Calculation For Complex Fourier
Series

6. Earlier computer to do research in DSP

7. DSP community
• With in last 30 years sharing of ideas between DSP research and
• Earlier with the advancement, microprocessors were
to do some simple DSP tasks in real time
Mini computers and Array processors were state of
DSP research community
the choice
• the art for
• Breakthrough
combination of
that made the DSP possible
hardware
was the
a microprocessor and a multiplier
• in 30
circuit community and invention of transistor revolutionized the
world with commercially available DSP

8. and general urpos computer o array rocessor so
“That discipline which has allowed us to replace a circuit
previously composed of a capacitor and a resistor with
two anti-aliasing filters, an A-to-D and a D-to-A converter,
and
long as the signal we are interested in does not vary
too quickly.”
Dr. Tom Barnwell

9. A i t h l O l f ti bl t ff d
Voice band modems Hard Disk Drives and 3D Graphics were
successful commercial products using DSPs
The DSP revolution
• DSPs were primarily a university curiosity in the 1960s – a toy for
university professors to play with
In the 1970s, DSP became a military advantage
The 1980s experienced the introduction of the cost-effective DSP
•
•
The 1990s, which can best be described as the decade of
consumer expansion Digital Cellular Phone can be the
best example
Now in 21st century DSP is every where
•

10. voice communications digital
e
Impact on Society
• The first wave of the revolution was, and continues to be,
communications
•
•
Analog wire-lined world of communications became digital
voice communications digital
• Industry moved from 2400 bps modems to 56K bps
band modems
• Digital Cell Phone everywher
802.11
DSL
Bluetooth
voice
•
•
•

11. TV
• The second wave of the revolution is entertainment
•
•
•
•
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Music
Photo
TV
Games
Radio
Streaming Media, combination of Digital Communication and Digital
Entertainment
And all in the pocket same time
•

12. without humane intervention
• What could be the next wave of revolution
• Transportation
• It is a matter of time when your car will drive from point A to B
without humane intervention
Biomedical Science
• Higher quality life of a deaf man with Cochlear implant
Education
• But there will be better uses
in the classrooms as well
•
•

13. What is DSP ?
Digital Signal Processing (DSP) is used in a wide variety of applications,
and it is hard to find a good definition that is general.
changing or analyzing information which is measured as
discrete sequences of numbers
TMS320C25 DSP

14. DSP Algorithm
TMS320C25 DSP
Example : Digital Filters (e.g. Digital FIR Filters ,...)
Most share common features:
•They use a lot of maths (multiplying and adding signals)
•They deal with signals that come from the real world
•They require a response in a certain time

15. Why DSP Processors?
A Comparison :
As shown ,DSP Processors are more efficient
TMS320C25 DSP

16. TMS320C25 DSP
Why DSP Processors? (Contd.)
As in FIR Filters

17. Why DSP is different than other Processors

18. System
Some Basic Characteristics
System
of a DSP
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Sampled data system
Intensive mathematics
Real time
Deterministic
Interrupt handling
Accuracy
Special hardware

19. •
Sampled Data system
• The signal must be sampled at twice the max frequency in the
signal known as Nyquist Freqency
Intensive Mathematics
• Most of the time in Signal Processing we do Filtering or
Transforms
•
•
Demand for lot of MAC operations
Following is a simple filter equation
•
•
For 100 tap FIR filter 100 MAC operations are needed
For 25 1080p frames per Sec a 50 tap filter needs to do 2.5 million
MACs per Sec for audio signal

20. Real Time
• For every input sample there is an output sample
• Latency, how much is the delay between input and its relative
output
• Easiest example is audio recording. Musician has an ear piece to
listen himself and others. The delay should be less than 5ms to
consider it to be real time
Deterministic
• Instruction execution time must be same every time independent
of data or state of execution unit
• Predictability to estimate the capability of DSP to meet the
demands early in the design cycle

21. the principle that real time systems cannot be interrupted
Interrupt handling
• This feature was added with the concept that interrupts are
entertained until the real time behavior is not effected to stick to
the principle that real time systems cannot
Accurate
• Accuracy is signal dependent
• Three basic concepts to know here are
interrupted
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SNR which is data accuracy. Simple relation is 6dB per bit
Coefficient accuracy is important in filters
Internal Accuracy

23. L H d t f th DSP l ith titi h
Special hardware
• To meet the needs of real time systems special hardwares that
DSPs have include are
• Loop Hardware as most of the DSP algorithms are repetitive such
FIR or FFT
Data memory management as DSP algorithms often rely on present
and past values of input data
Saturation logic to keep the numbers inside the bound. If result
exceeds the bounds maximum +ve or –ve number is assigned
• E.g. scale all the data and coefficients to keep the results with in
+1 and -1. But multiple MACs may yield the result out of this
bound so the concept of guard bits in accumulator was
developed
Multi-MAC units executing in parallel has increased the perforamance
of DSP rapidly over the last couple of decades
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•