Motorola DSP56000 User Manual

 

MOTOROLA

The equivalent circuit using a DSP is shown in Figure 1-2. This application requires an
analog-to-digital (A/D) converter and digital-to-analog (D/A) converter in addition to the
DSP. Even with these additional parts, the component count can be lower using a DSP
due to the high integration available with current components.

Processing in this circuit begins by band-limiting the input with an anti-alias filter, eliminat-
ing out-of-band signals that can be aliased back into the pass band due to the sampling
process. The signal is then sampled, digitized with an A/D converter, and sent to the DSP.

The filter implemented by the DSP is strictly a matter of software. The DSP can directly
implement any filter that can also be implemented using analog techniques. Also, adap-
tive filters can be easily implemented using DSP, whereas these filters are extremely
difficult to implement using analog techniques.

The DSP output is processed by a D/A converter and is low-pass filtered to remove the
effects of digitizing. In summary, the advantages of using the DSP include the following:

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1

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y(t)

OUTPUT

TO

ACTUATOR

t

x(t)

INPUT

FROM

SENSOR

x(t)

R

i

R

f

C

f

IDEAL

FILTER

f

f

c

FREQUENCY

GAIN

y(t)