IEEE Electrification Magazine - December 2017 - 49

In the aerospace
industry, a major
aspect of choosing
a component is
technology readiness,
i.e., the maturity
of the concept
and hardware.

increases the speed of computations
and command executions while
allowing higher control flexibilities
and complex systems control. A
modular and model-based design
approach, in which the CCPS is
divided into modules, can be
applied. This allows flexibility to
meet different applications and
simplifies the design. In modelbased schemes, a system archetype
is at the center of the development
process from requirements through
to design, implementation, and testing. This model-based design
enables the fast and cost-effective generation of dynamic
control systems, signal processing, communications systems, and so on.

ARM-Based Microprocessors
for Avionic Application
The ARM processor was the outcome of a project within
Acorn's advanced research and development section, with
the first samples delivered in 1985. The ARM is an RISC
processor architecture currently developed by ARM Holdings and licensed to other companies. By licensing the
architecture instead of manufacturing the actual chip, ARM
Holdings created a new business model for the industry.
Unlike complex instruction-set computing, RISC is based
on simplified instruction sets that provide higher performance when combined with a microprocessor architecture
capable of executing commands in fewer microprocessor
cycles per instruction. ARM-based processors are simple in
structure and, compared to general-purpose microprocessors, have a relatively small number of transistors, which
thus allows other modules to be included on the chip.
Therefore, due to its modular design, an ARM processor
may consist of mandatory pipelines, caches, memory
management units (MMUs), floating-point units, and
coprocessors. This provides flexibility for developing application-specific ARM processors. The ARM processors and
their pipelines are designed for minimized energy consumption that is suitable for embedded systems, and they
are small in size while providing high performance. The
ARM processors commonly use variable execution time,
subword parallelism, digital-signal-processor-like operations, thread-level parallelism and exception handling, and
multiprocessing, which make these processors efficient
with high-performance capability. The ARM has a loadstore architecture, i.e., the ARM processor first loads the
data to one of the general-purpose registers before processing it. Therefore, commands in the ARM instruction
set the architecture load and store multiple registers with
variable cycles to execute, as compared to individually
loading and storing each register in RISC systems. This
improves code density, reduces instruction fetches, and

lowers overall power consumption.
Figure 3 shows the structure of an
ARM Cortex microprocessor. ARM
Holdings currently develops three
different profiles for the ARM architecture, i.e., ARM Cortex-A (the application profile), ARM Cortex-R (the
real-time profile), and ARM Cortex-M
(the microcontroller profile).
ARM Cortex-R processors offer
high-performance computing and
deliver fast deterministic processing
for systems where reliability, high
availability, fault tolerance, and
maintainability are demanded. The
Cortex-R processors provide fast time-to-market, and they
are popular in real-time and embedded applications such
as automotive safety, storage, and wireless basebands. The
Cortex-R series can be separated into two different types:
real-time processors that focus on efficiency and real-time
processors that focus on performance.
The Cortex-M family offers a low-cost and power- and
energy-efficient solution suitable for embedded-system
applications such as the Internet of Things (IoT), connectivity, motor control, smart metering, human-interface
devices, automotive and industrial control systems,
domestic household appliances, consumer products,
and medical instrumentation. The Cortex-M series
of processors can be separated into two different
types: 1) processors built with a focus on minimum
power and area and 2) processors built with a focus
on performance efficiency.

ADC

I/O Ports

Debug
Run-Ctrl

Timer/
Counter

Interrupt
System

Debug
Channel

PWM

Flash
ROM

ARM
CPU

UART
I2C/SPI

Ethernet

RAM
DMA

SD/MMC
Interface

Real-Time
Clock

USB

CAN

Figure 3. An ARM cortex microprocessor. I/O: input-output; ctrl: control; PWM: pulse-width modulator; ROM: read-only memory; UART: universal asynchronous receiver-transmitter; DMA: direct memory access;
I2C: interintegrated circuit; USB: universal serial bus; SD: secure
digital; MMC: multimedia card; CAN: controller area network.

IEEE Electrific ation Magazine / D EC EM BE R 2 0 1 7

Table of Contents for the Digital Edition of IEEE Electrification Magazine - December 2017