The PLD Advantage
Fixed logic devices and PLDs both have their
advantages. Fixed logic devices, for example, are often more appropriate for
large volume applications because they can be mass-produced more economically.
For certain applications where the very highest performance is required, fixed
logic devices may also be the best choice.
However, programmable logic devices offer a
number of important advantages over fixed logic devices, including:
customers much more flexibility during the design cycle because design
iterations are simply a matter of changing the programming file, and the
results of design changes can be seen immediately in
not require long lead times for prototypes or production parts - the PLDs are already on a distributor's shelf and ready for shipment.
not require customers to pay for large NRE costs and purchase expensive mask
sets - PLD suppliers incur those costs when they design their programmable
devices and are able to amortize those costs over the multi-year lifespan of a
given line of PLDs.
customers to order just the number of parts they need, when they need them,
allowing them to control inventory. Customers who use fixed logic devices often
end up with excess inventory which must be scrapped, or if demand for their product surges, they may be caught short of parts and face production
be reprogrammed even after a piece of equipment is shipped to a customer. In
fact, thanks to programmable logic devices, a number of equipment manufacturers
now tout the ability to add new features or upgrade products that already are
in the field. To do this, they simply upload a new programming file to the PLD,
via the Internet, creating new hardware logic in the system.
Over the last few years programmable logic
suppliers have made such phenomenal technical advances that PLDs are now seen
as the logic solution of choice from many designers. One reasons for this is
that PLD suppliers such as Xilinx are "fabless" companies; instead of
owning chip manufacturing foundries, Xilinx out sources that job to partners
like IBM Microelectronics and UMC, whose chief occupation is making chips. This
strategy allows Xilinx to focus on designing new product architectures,
software tools, and intellectual property cores while having access to the most
advanced semiconductor process technologies. Advanced process technologies help
PLDs in a number of key areas: faster performance, integration of more
features, reduced power consumption, and lower cost. Today Xilinx is producing
programmable logic devices on a state-of-the-art 0.13-micron low-k copper
process - one of the best in the industry.
Just a few years ago, for example, the largest
FPGA was measured in tens of thousands of system gates and operated at 40 MHz.
Older FPGAs also were relatively expensive, costing often more than $150 for
the most advanced parts at the time. Today, however, FPGAs with advanced
features offer millions of gates of logic capacity, operate at 300 MHz, can
cost less than $10, and offer a new level of integrated functions such as
processors and memory.
Just as significant, PLDs now have a growing
library of intellectual property (IP) or cores - these are predefined and
tested software modules that customer can use to create system functions
instantly inside the PLD. Cores include everything from complex digital signal
processing algorithms and memory controllers to bus interfaces and full-blown
software-based microprocessors. Such cores save customers a lot of time and
expense --it would take customers months to create these functions, further
delaying a product introduction.