Software engineering for real-time systems

Transcription

1 Introduction Software engineering for real-time systems Objectives To: Section 1 Introduction to real-time systems Outline the differences between general-purpose 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 s. Describe the structures of modern microprocessors and micros. SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 1 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 2 A modern batch system Typical interactive on-line system Local multiplexer Site 1 Local site Remote site Remote site Central (mainframe) Fibre-optic data link Local multiplexer Site 2 Fibre-optic communication unit Fibre-optic communication unit Cray super SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 3 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 4 A real-time system Categorizing real-time systems Control panel SLOW FAST SOFT Machinery condition monitoring Man-Machine Interfacing Control Power unit Vehicle sensors 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 5 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 6 1

2 Attributes of real-time systems Telemetry control system Execution Deadlines Software Software time size complexity Hard - Fast Hard - Slow Soft - Fast Soft - Slow Remote plant 1 Microprocessor-based outstation Sensors Data collection Control functions Actuators Communication Remote plant 2 Wireless communication link (100 miles) Attribute rating Low high 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). Land line communication link (10 miles) Central control room Front-end communication Main control Hot standby control Local area network Management Operator display Data logging information and controls SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 7 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 8 Sea Skua missile system Submarine control console SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 9 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 10 Typical avionic platforms Microprocessor-based vending machine units SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 11 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 12 2

3 Consumer communications Embedded systems platforms Embedded systems platforms Bespoke designs Commercial off the shelf (COTS) equipment Board-based designs PC-based designs Vendor specific VME PC/104 Embedded PC Desktop PC Ruggedized PC SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 13 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 14 Embedded systems characteristics Typical temperature specifications for real-time systems Embedded systems characteristics Defined by Environment Performance Interfacing Degrees centigrade Industrial range Extended industrial range Physical Electricial Operational Speed of response Failure modes Military range Oil exploration Space exploration SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 15 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 16 Computer loading - single synchronous (periodic) task Computer loading - single asynchronous (aperiodic) task T e T e T e Execute event task (E) processor idle (I) Execute event task (E) (I) Execute event task (E) (I) Time Event signal Event signal Event signal SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 17 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 18 3

4 Computer loading - multiple asynchronous (aperiodic) tasks The computing elements of real-time systems (E1) = Event task 1 execution (E2) = Event task 2 execution (S1) = Event signal, task1 (S2) = Event signal, task 2 (I) = Idle (spare) time (W) = waiting time for task to complete (W) (E 1 ) (I) (E 1 ) (I) (E 2 ) (I) (E 1 ) (I) (E 1 ) (E 2 ) Time Computing elements General purpose computing Microprocessors Micros Digital signal General purpose Highly integrated Single chip Single chip processors microprocessors microprocessors micros micros (DSPs) Specialized computing Bespoke Mixed signal system-on-chip processors designs S 1 S 1 S 1 S 1 S 2 S 2 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 19 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 20 Elements of a micro system Timing in hardware Real-time clock Programmable timer To interrupt Control Chip select line SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 21 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 22 The watchdog timer operation Write control decoder I/P Retriggerable timer (monostable) O/P To non-maskable interrupt External alarm (optional) Timeout Processor hold/ack Micro ROM Peripheral (a) Normal mode of operation request/ack O/P I/P ROM Peripheral request/ack Time (B) Fig.1.21 mode operation of operation SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 23 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 24 4

5 Intelligent I/O processing I/O peripheral Local memory Main processor and control and control Programmable command register I/O port 8 lines Disk store Primary I/O processor Secondary Data Data buffer I/O port I/O port 8 lines 8 lines SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 25 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 26 Highly integrated processor -Motorola MPC8240 Single chip micro - Philips Semiconductor 8052 Intelligent message (I 2 O) PowerPC 603e microprocessor core (including floating point maths unit) Clock Processor Hardware timers (3) I 2 C Interrupts Serial comms (I 2 C) Interrupt and timers Central control unit PCI unit Data path Memory PCI arbiter Data Memory Security ROM Program store (8kByte ROM) Data store (256 Bytes ) Interrupt Serial communication I/O ports (4) PCI Bus Bus request grant (5) (5) External SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 27 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 28 Single chip micro - Fujitsu MB91F361 Digital signal processor structure Processor unit CPU Watchdog Interrupt Data (16 kbyte) Cache memory (1 kbyte) Sound generator LED driver GP Serial I/O I 2 C serial Boot ROM (2 kbyte) ADC (16) DAC (2) Bus Interrupt (8) CAN (3) Stepper motor control Real-time clock Flash (512 kbyte) Hardware timers (6) Pulse generator External Digital I/0 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 29 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 30 5

6 Mixed signal processor structure - Texas MSP430 Example system-on-a-chip (SOC) design Clock CPU (256 bytes) Debug Analogue comparator Custom coprocessor Processor core Custom I/O Custom peripherals and debug External Flash (256 bytes) Ports with interrupt facility (2) Custom MMU Power-on reset Watchdog timer PWM Timer ROM On-chip data (OCB) Custom powermanagement unit SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 31 SOFTWARE ENGINEERING for REAL-TIME SYSTEMS ( J.E.Cooling 2003) Introduction to real-time systems - slide 32 Review of Introduction to real-time systems Review of section You should now: 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 units. Appreciate the essential differences between microprocessors, micros and micros. 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 6