Software engineering for real-time systems

Software engineering for real-time systems
Section 1
Introduction to real-time systems
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 1
Fibre-optic
communication unit
A modern batch system
Local site
Fibre-optic
data link
Remote site
Fibre-optic
communication unit
Cray
supercomputer
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 3
Control panel
A real-time computer system
Control
computer
Power unit
Vehicle
sensors
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 5
Introduction
Objectives
To:
• Outline the differences between general-purpose
computer applications and real-time systems.
Give an overview of practical real-time system
structures.
Describe some key environmental and performance
requirements of embedded real-time computers.
Describe the structures of modern microprocessors
and microcomputers.
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 2
Local
multiplexer
Local
multiplexer
Typical interactive on-line computer system
Site 1
Site 2
Remote site
Central
(mainframe)
computer
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 4
Categorizing real-time systems
SLOW FAST
SOFT Machinery condition monitoring Man-Machine Interfacing
HARD Missile point defence system Airbag control system
Two major categorization factors: criticality and speed.
Criticality:
Hard systems - deadlines (responsiveness) is critical. Failure to meet these
have severe consequences (e.g. injury, damage or death).
Soft systems - deadlines are less critical; in many cases significant
tolerance can be permitted.
Speed:
– Fast systems - responses in the microseconds to hundreds of milliseconds.
– Slow systems - responses in the range seconds to days.
– Arbitrary boundary: 1 second (chosen because the problems shift from
individual computing issues to overall system behaviour and interaction at
around this point).
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 6
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Execution Deadlines Software Software
time
size
complexity
Hard - Fast
Hard - Slow
Soft - Fast
Soft - Slow
Attribute rating
Low high
Attributes of real-time systems
Major attributes of real-time systems.
For hard systems emphasis is placed on the need to meet deadlines.
Hard-fast systems tend to have low software complexity.
For soft-fast systems emphasis is put on computation performance.
In general soft systems tend to be the more complex ones (from a software
perspective).
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 7
Sea Skua missile system
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 9
Typical avionic platforms
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 11
Remote plant 1
Sensors
Actuators
Microprocessor-based outstation
Data collection
Control functions
Communication interface
Land line
communication link
(10 miles)
Central control
room
Telemetry control system
Main control
computer
Local area network
Operator display
and controls
Front-end
communication
interface
Data logging
computer
Wireless
communication link
(100 miles)
Hot standby
control computer
Management
information
computer
Remote
plant 2
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 8
Submarine control console
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 10
Microprocessor-based vending machine units
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 12
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Consumer communications
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 13
Embedded systems characteristics
Embedded systems
characteristics
Defined by
Environment Performance Interfacing
Physical Electricial Operational Speed of
response
Failure
modes
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 15
Computer loading - single synchronous (periodic) task
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 17
Vendor
specific
Bespoke designs
Board-based
designs
VME
Embedded systems platforms
Embedded systems
platforms
PC/104
Embedded PC
Commercial off the shelf
(COTS) equipment
PC-based
designs
Desktop
PC
Ruggedized
PC
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 14
Typical temperature specifications for real-time systems
Degrees centigrade
-55 0 +50 +85 +125 +200
Industrial
range
Extended industrial
range
Military range
Oil exploration
Space exploration
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 16
Event
signal
Computer loading - single asynchronous (aperiodic) task
T e T e T e
Execute
event task
(E)
processor idle (I)
Event
signal
Execute
event task
(E)
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 18
(I)
Event
signal
Execute
event task
(E)
Time
(I)
3

S 1
Computer loading - multiple asynchronous (aperiodic) tasks
(E1) = Event task 1 execution
(E2) = Event task 2 execution
(S1) = Event signal, task1
(S2) = Event signal, task 2
(I) = Idle (spare) time
(E (I)
1 ) (I) (E1 ) (I) (E2 )
(E1 ) (I) (E1 ) (E2 )
S 1
S 2
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 19
S 1
(W) = waiting time for task to
complete
(W)
S 1
S 2
Time
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 21
Write
control
Address
bus
O/P
I/P
Address
decoder
Elements of a microcomputer system
I/P
The watchdog timer
Retriggerable timer
(monostable)
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 23
O/P
To non-maskable interrupt
External alarm (optional)
Timeout
Time
General purpose
microprocessors
General purpose computing
Microprocessors Microcomputers
Highly integrated
microprocessors
The computing elements of real-time systems
Single chip
microcomputers
Computing elements
Single chip
microcontrollers
Digital signal
processors
(DSPs)
Specialized computing
Mixed signal
processors
Bespoke
system-on-chip
designs
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 20
Timing in hardware
Real-time clock Programmable timer
Control
bus
Address
bus
Chip
select
line
To
interrupt
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 22
Micro
ROM
RAM
(a) Normal mode
of operation
ROM
RAM
DMA operation
Processor hold/ack
DMA
controller
Peripheral
interface
DMA
controller
Peripheral
interface
(B) DMA Fig.1.21 mode DMA operation
of operation
DMA
request/ack
DMA
request/ack
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 24
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SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 25
I 2 C bus
Interrupts
Local
memory
Disk store
Intelligent
message
controller
(I 2 O)
DMA
controller
Serial
comms
controller
(I 2 C)
Interrupt
controller and
timers
Intelligent I/O processing
Primary
bus
Main
processor
I/O processor
Highly integrated processor -Motorola MPC8240
Secondary
bus
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 27
External
bus
PowerPC 603e
microprocessor core
(including floating point
maths unit)
Central
control unit
PCI bus interface
unit
PCI bus
Data path
controller
Memory
controller
PCI bus
arbiter
Bus
request
(5)
Bus
grant
(5)
Single chip microcontroller - Fujitsu MB91F361
Processor unit
CPU
Watchdog
Interrupt controller
Data RAM (16 kByte)
DMA
Cache memory (1
kByte)
Boot ROM (2 kByte)
CAN
interface
(3)
Flash
(512
kByte)
Bus
interface
Sound generator
LED driver
GP Serial I/O
I 2 C serial
interface
ADC (16)
DAC (2)
Interrupt
interface (8)
Stepper motor
control
Real-time clock
Hardware timers
(6)
Pulse generator
Digital I/0
Data
bus
Memory
bus
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 29
Address
and control
bus
Data
bus
Programmable
command
register
Data bus buffer
I/O interface peripheral
Address and
control interface
I/O port
I/O port
I/O port
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 26
Single chip microcomputer - Philips Semiconductor 8052
Clock
Processor
Security ROM
Program store
(8kByte ROM)
Data store
(256 Bytes RAM)
External bus
Hardware timers
(3)
Interrupt
controller
Serial
communication
controller
I/O ports (4)
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 28
Digital signal processor structure
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 30
8 lines
8 lines
8 lines
5

SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 31
You should now:
Mixed signal processor structure - Texas MSP430
Clock
CPU
RAM
(256 bytes)
Flash
(256 bytes)
Power-on
reset
Watchdog
timer
Debug
interface
Analogue
comparator
Ports with
interrupt
facility (2)
PWM
Timer
Review of ‘Introduction to real-time systems’
Review of section
• Clearly understand the important features of real-time systems.
• Know what sets them apart from batch and interactive application.
• See how real-time systems may be categorized in terms of speed and criticality.
• Have a general understanding of the range of real-time (and especially embedded)
applications.
• Realize that environmental and performance factors are key drivers in real-time
systems design.
• Know the basic component parts of real-time computer units.
• Appreciate the essential differences between microprocessors, microcomputers and
microcontrollers.
• Realize why there is a large market for specialized processors.
END OF SECTION ‘Introduction to real-time systems’
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 33
Example system-on-a-chip (SOC) design
Custom coprocessor
Processor
core
RAM
ROM
On-chip databus (OCB)
Custom I/O
interface
Custom
peripherals
and debug
interface
Custom
MMU
Custom powermanagement
unit
External
bus
SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 32
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