Digital Signal Processing Reference
In-Depth Information
or EEPROM) is used for the permanent storage of the application program. The
bootloader program can be modified to initialize the system, retrieve a program
from non-volatile memory, store it in the faster, volatile memory, and then start
it executing from the faster memory. This scheme provides the advantages of
permanent storage, fast execution, and the ability to modify the application
program when needed. Of course, it comes at the expense of having additional
memory.
To P C
(via Serial Interface)
FPGA
Volatile M em ory
(for Application
Program Execution)
Onchip Memory
(Initialized with
bootloader)
Processor
Core
Nonvolatile Memory
(for Application
Program Storage)
Figure 15.2
This arrangement of on-chip and external memories provides flexibility and
performance to an SOPC system.
15.4 SOPC Design versus Traditional Design Modalities
The traditional design modalities are ASIC and fixed-processor design. SOPC
design has advantages and disadvantages to both of these alternatives as
highlighted in Table 15.2. The strengths of SOPC design are a reconfigurable,
flexible nature and the short development cycle. However, the trade offs
include lower maximum performance, higher unit costs in production, and
relatively high power consumption.
The benefit of having a flexible hardware infrastructure can not be
overestimated. In many new designs, features and specifications are modified
throughout the design cycle. For example, marketing may detect a shift in
demand requiring additional features (e.g., demand drops for cell phones
without cameras), a protocol or specification is updated (e.g., USB 2.0 is
introduced), or the customer requests an additional feature. In traditional design
modalities (including ASIC and fixed-processor designs), these changes can
dramatically effect the ASIC design, processor selection, and/or printed circuit
board design. Since the hardware architecture is often settled upon early in the
design cycle, making changes to the hardware design later in the cycle will
typically result in delaying a product's release and increasing its cost.
Flexible infrastructure can also be beneficial in extending the life (and thus
reducing the cost) of a product's hardware. With flexible, reconfigurable logic,
often a single printed circuit board can be designed that can be used in multiple
product lines and in multiple generations/versions of a single product. Using
