Diversity and Multi-Version Systems - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 186

AN EVOLUTION OF FPGA
TECHNOLOGY AND DIVERSITY
APPLICATION IN NPP I&CS

so called heterosystems - systems with a “fuzzy”
software-hardware architecture and mixed execu-
tion of functions. This circumstance and other
features of FPGA technology increase a number
of diversity types and enlarge a set of possible
diversity-oriented decisions for NPP I&Cs.

Complex Electronic Components
and FPGA Technology for
NPP I&Cs Development

FPGA Peculiarities in Context
of Dependability and Safety

An analysis of development and introduction
trends of computer technologies to NPP I&Cs
has specified a number of important aspects af-
fecting their safety, peculiarities of development,
update and licensing. Such trends include, among
others (Yastrebenetsky, 2004): introduction of
novel complex electronic components (CECs);
expanded nomenclature of a software applied
and increased effect of its quality to I&Cs safety;
realization of novel principles and technologies
in I&Cs development; advent of a large number
of novel standards regulating the processes of
I&Cs development and safety assessment. During
recent decades the application of microprocessor
techniques in NPP I&Cs design has substantially
expanded. Microprocessors are used both in a sys-
tem computer core and in realization of intellectual
peripherals - various sensors, drives and other
devices with built-in programmable controllers.
Another contemporary trend is dynami-
cally growing application of programmable logic
technologies, particularly, FPGA in NPP I&Cs,
onboard aerospace systems and other critical
areas. FPGA as a kind of CECs is a convenient
mean not only in realization of auxiliary func-
tions of transformation and logical processing
of information, but also in execution of basic
monitoring and control functions inherent in
NPP I&Cs. This approach in some cases is more
reasonable than application of software-controlled
microprocessors (Kharchenko&Sklyar, 2008).
In assessment of FPGA-based I&Cs it should be
taken into consideration that application of this
technologies somewhat levels the difference be-
tween hardware and software, whereas obtained
solutions are an example of a peculiar realization of

FPGA architecture topologically originates from
channeled Gates Arrays (GA). In FPGA internal
area a set of configurable logic units is disposed
in a regular order with routing channels there
between and I/O units at the periphery. Transis-
tor couples, logic gates NAND, NOR (Simple
Logic Cell), multiplexer-based logic modules,
logic modules based on programmable Look-
Up Tables (LUT) are used as configurable logic
blocks. All those have segmented architecture of
internal connections.
System-On-Chip architecture appeared due
to two factors: a high level of integration permit-
ting to arrange a very complicated circuit on a
single crystal, and an introduction of specialized
hardcores into FPGA. Additional hardcores may
be: additional Random Access Memory (RAM)
units; JTAG interface for testing and configurating;
Phase-Locked Loop (PLL) - a frequency control
system to correct timing relations of clock pulses
as well as for generation of additional frequencies;
processor cores enabling creation of devices with
a control processor and a peripheral.
An analysis of dependability assurance
possibilities in FPGA-based systems permit to
determine the following FPGA peculiarities
(Kharchenko & Sklyar, 2008; Bobrek et al., 2009).

1. Simplification of development and verifica-
tion processes: an apparatus parallelism in
control algorithms execution and realization
of different functions by different FPGA ele-
ments; an absence of cyclical structures in
FPGA projects; an identity of FPGA project