# Standard Operating Procedure
**Document Number:** ROBOT-SYS-001  
**Standard Operating Procedure (SOP):** Real-Time Robotics Controller Task Scheduler  
**Revision:** 1.0  
**Last Updated:** [DATE]

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## Contents

1. Introduction  
    1.1 Purpose  
    1.2 System Overview  
    1.3 Regulatory Compliance  

2. System Specifications  
    2.1 Task Definitions and Parameters  
    2.2 System Timer Configuration  

3. Operational Protocols  
    3.1 Standard Operating Procedures  
        3.1.1 Task Execution Cycle  
        3.1.2 Processor Assignment Policy  
    3.2 Performance Optimization  
        3.2.1 Overlap Avoidance  
        3.2.2 Priority Scheduling  

4. Emergency Operations  
    4.1 Task Starvation and Data Staleness  
    4.2 Recovery From Timeout Skew  

5. Maintenance Requirements  
    5.1 Task Reset Logic  
    5.2 Priority Conflict Testing  

6. Quality Assurance  
    6.1 Execution Integrity Checks  
    6.2 Latency Verification  

7. Security Protocols  
    7.1 Resource Isolation  
    7.2 Task Conflict Resolution  

8. Environmental Considerations  
    8.1 Real-Time Synchronization Margin  
    8.2 Resource Load Handling  

9. Training Requirements  
    9.1 System Familiarity  
    9.2 Debugging and Profiling  

10. Document Control  
    10.1 Revision History  
    10.2 Authorization  

11. Process Flows and State Transitions  
    11.1 Task Workflow Summary  
    11.2 Arbitration and Processor Grant Logic  
    11.3 Timeout Triggering Logic  

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## 1. Introduction

### 1.1 Purpose
To manage real-time task execution in a robotics controller by coordinating periodic processes across sensor, motor, and communication modules.

### 1.2 System Overview
- Executes five periodic tasks (T1–T5) with distinct timing and resource needs.
- Schedules tasks by priority and processor availability.
- Uses shared arbitration to ensure fair, conflict-free task execution.

### 1.3 Regulatory Compliance
- Complies with embedded robotics system timing requirements.
- Ensures no starvation and bounded response latency.

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## 2. System Specifications

### 2.1 Task Definitions and Parameters
- **T1 (Motor control):** Period 40ms; Execution 1ms (pri10), 5ms (pri7)
- **T2 (Sensor read):** Period 100ms; Execution 10ms (pri4), 5ms (pri8), 5ms (pri4)
- **T3 (Sensor control):** Offset 50ms; Execution 8ms (pri5), 12ms (pri8)
- **T4 (Comm read):** Period 200ms; Execution 10ms (pri9), 20ms (pri2), 3ms (pri3)
- **T5 (Comm process):** Period 400ms; Execution 2ms (pri3), 12ms (pri1), 10ms (pri6)

### 2.2 System Timer Configuration
- Timer values used to generate timeouts:
    - `timeout40`, `timeout50`, `timeout100`, `timeout100offset`, `timeout200`, `timeout400`
- Timers trigger request logic in each module.

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## 3. Operational Protocols

### 3.1 Standard Operating Procedures

#### 3.1.1 Task Execution Cycle
- Tasks begin in `state = 0`
- On timeout, `start` flag is activated
- Progresses through multiple execution states until `finish = TRUE`
- Resets to idle state after each full cycle

#### 3.1.2 Processor Assignment Policy
- Each task submits a `request` signal based on its priority
- Central scheduler grants processor access to task with highest priority
- Tie cases (e.g., T2 vs T3) resolved using `last24` flag toggle logic

### 3.2 Performance Optimization

#### 3.2.1 Overlap Avoidance
- Task activations blocked if prior activation not yet complete
- `error` condition raised if timeout triggers while task is active

#### 3.2.2 Priority Scheduling
- Grant assigned to task with maximum request value
- Conflicts resolved with fixed arbitration rules and toggled preference bit

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## 4. Emergency Operations

### 4.1 Task Starvation and Data Staleness
- T3 includes `activation_count` tracking number of times it’s triggered
- May decline to execute if T2 has not generated sufficient new data

### 4.2 Recovery From Timeout Skew
- On invalid activation conditions, task remains idle
- Task resumes execution in next cycle if valid trigger conditions restored

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## 5. Maintenance Requirements

### 5.1 Task Reset Logic
- On `finish`, reset internal `state` to 0
- Counters and latches (e.g., `activation_count`, `timeoutlatch`) also reset

### 5.2 Priority Conflict Testing
- Validate arbitration fairness with priority collision simulations
- Specifically check interactions between T2/T3 and T4/T5

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## 6. Quality Assurance

### 6.1 Execution Integrity Checks
- Assert single task execution per processor at any time
- Check `error` flag during all timeout conditions

### 6.2 Latency Verification
- Calculate response time: `MIN[start, finish]` and `MAX[start, finish]`
- Check how quickly T3 responds after T2 finishes

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## 7. Security Protocols

### 7.1 Resource Isolation
- One processor-granted task at a time
- Scheduler prevents concurrent use of shared processor

### 7.2 Task Conflict Resolution
- `last24` toggled based on most recent winner between T2/T3 or T4/T5
- Ensures both tasks get fair turns over time

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## 8. Environmental Considerations

### 8.1 Real-Time Synchronization Margin
- Comm and sensor operations aligned via timeout offsets
- Avoids sensor/motor control timing mismatches

### 8.2 Resource Load Handling
- Cooldown periods implied by timeout intervals and activation counters
- Prevents overloading processor under bursty input

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## 9. Training Requirements

### 9.1 System Familiarity
- Operators must understand timing, state transitions, and arbitration logic
- Maintenance staff must interpret latch/counter behavior

### 9.2 Debugging and Profiling
- Review logs from timeout-based activations
- Profile arbitration performance and latency across T1–T5

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## 10. Document Control

### 10.1 Revision History
- Rev 1.0 – Initial SOP derived from formal model (robot.txt)

### 10.2 Authorization
- Approved by: Embedded Systems Lead  
- Reviewed by: Real-Time Safety Board

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## 11. Process Flows and State Transitions

### 11.1 Task Workflow Summary
- All tasks follow: `idle → executing → finished → idle`
- Reentry triggered by timer events

### 11.2 Arbitration and Processor Grant Logic
- Scheduler compares request values across tasks
- Chooses winner or toggles `last24` to resolve ties

### 11.3 Timeout Triggering Logic
- Timeouts fire at fixed modular intervals (40ms, 50ms, etc.)
- Used to synchronize task startups and control latency margins