November 15, 2017 Sam Siewert

CEC450 Real-Time Systems

Lecture 15 – Block Diagram Design Examples

Design Elements for Proof-of-Concept Top N Capability Oriented Requirements – State and Explain – Hold Q&A and Ask for Reviewer Input on Completeness, Errors and

Omissions

Top N Real-Time Requirements [Ci, Ti, Di or each Si] – State and Explain Service request frequency drivers and relative deadlines – How did you estimate or measure Ci WCET

Single Page High Level Block Diagram of Software System – Show End-to-End Elements and Dataflow – Source to Sink (Top Left Corner to Bottom Right)

CFD/DFD, Flow Charts, State Machines or Other Design Models Proof-of-Concept Time-Stamp Tracing Analysis Sam Siewert 2

Design Example

STS-85 Payload (Flown 1997, U. of Colorado)

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Payload Operations 1. The Embedded System Shall Operate 3 Instruments (LASIT, SXEE, FARUS) According

to a Scheduled Observing Plan of the Sun within STS Imposed Constraints 2. The Health & Status of Each Instrument Shall be Reported to the Ground Continuously 3. Science Data Collected by Each Instrument Shall be Streamed to the Ground While an

Instrument is Observing 4. Observing Plan Updates Can be Uplinked from the Ground Systems as Command(s) with

Response 5. Commands to Operate Instruments Interactively Can be Uplinked from the Ground and

Status Indication Response Will be Provided 6. The Embedded System Must Interface to Low-Rate Uplink and Downlink interfaces on

STS for Command/Response, H&S Telemetry Streaming 7. The Ground Software at GSFC Must Interface to the ACCESS LRDU 8. Telemetry Must be Stored in a Time-stamped Database 9. A HMI GUI Must Display H&S Telemetry at GSFC and Provide a Command/Response

Interface 10. GSFC Ground Systems Must Host a Planning and Operations Rules and Constraints

Database and Engine 11. GSFC Ground Systems Must Host H&S Telemetry Monitoring to Detect Anomalous

Behavior to Generate Alerts for the HMI/GUI 12. A Data Bridge Between GSFC Ground Systems and CU Boulder Must Provide a

Command/Response and H&S Telemetry Network Interface 13. CU Boulder Ground Systems Must Interface an Automated Planning and Scheduling

Software Application and Allow it to Generate Uplink Commands to Modify or Replace the Current Embedded System Observing Plan

14. The CU Boulder Ground Systems Must Provide and HMI/GUI for H&S Telemetry, Command/Response and Automated Planning and Scheduling

15. A CU Boulder to NASA JPL Data Bridge Must Provide H&S Telemetry for Beacon Monitoring to NASA JPL for Display on a High Level Status HMI/GUI

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Hardware End-to-End System DATA Hitchhiker Payload, flown STS-85, Summer 1997 Designed, Built and Operated by U. of Colorado Students

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Software End-to-End System

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SE300 RT Design Models

Examples from SE300 (Specific to Real-Time Design)

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transformational processes, representing computations or information processing activities

control processes, representing system’s state dependent behavior, which is modeled by a Mealy type state machine

ordinary or discrete data flow

event flow or control flow that triggers a transition of the state machine of a control process, or a command from a control process to a transformational process

continuous data flow, which must be processed in real time

Real Time Systems Design

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Real Time Systems Design

a

b

P indicates that both data flow a and data flow b are required to begin executing process P

a

b

P indicates that either data flow a or data flow b is required to begin executing process P

+

These logical connector can be applied to both data flow and control flow and transformation process and control process.

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Real Time Systems Design

Z

Z

X

Y

Y

X Z

Z

Two subsets of Z are used by two different successor processes.

All of Z is used by two different successor processes.

Z is composed of Two subsets provided by two different predecessor processes.

All of Z is provided by either one of two predecessor processes.

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CFD/DFD Cruise Control Example

Cruise Control

2.2.1

Record Rotation

Rate 2.2.2

Increase Speed 2.2.3

Maintain Constant

Speed 2.2.4

Return to Previous

Speed 2.2.5

resume brake

enable/disable

start/stop increase speed

rotation rate trigger

speed reached

enable/ disable

throttle control

rotation rate

throttle position

rotation rate set point

rotation rate

throttle position

throttle control throttle

position

enable/ disable

rotation rate

enable/ disable

throttle control

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Maintain Speed

Increase Speed

Resume Speed

Interrupted

enable[] / trigger RRR; enable MCS

brake[] / disable MCS

stop increasing speed[] / disable IS; trigger RRR; enable MCS

brake[] / disable RPS resume[] / enable RPS

start increase speed[] / disable MCS; enable IS

brake[] / disable IS

speed reached[] / disable RPS; enable MCS

disable[] / disable MCS