Programmable Logic Devices
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+V
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Y
Figure 9.2 Simple programmable logic circuit.
9.1.1 Advantages and Disadvantages
1. If we want to build a fixed logic device to perform a certain specific function, the time required
from design to the final stage when the manufactured device is actually available for use could
easily be several months to a year or so. PLD-based design requires much less time from design
cycle to production run.
2. In the case of fixed logic devices, the process of design validation followed by incorporation
of changes, if any, involves substantial nonrecurring engineering (NRE) costs, which leads to an
enhanced cost of the initial prototype device. In the case of PLDs, inexpensive software tools can
be used for quick validation of designs. The programmable feature of these devices allows quick
incorporation of changes and also a quick testing of the device in an actual application environment.
In this case, the device used for prototyping is the same as the one that would qualify for use in the
end equipment.