# PFES-ENG-013 — Firmware Behavior

**Status:** Primary engineering objective  
**Knowledge Cycle Stages:** Understand, Validate

## Purpose

Describe what firmware does, including state transitions and externally observable effects, independently of exact implementation.

## Engineering Problem

Capabilities emerge from multiple routines, shared state, timers, and hardware interactions. Function discovery alone is insufficient.

## Historical Engineering Evolution

Project work shifted from locating handlers to reproducing behaviors such as Xbox authentication, media transitions, sticky descramble state, command routing, and tray logic.

## Engineering Discoveries

- Behavior survives implementation changes.
- Behavior is the strongest cross-family abstraction.

## Architectural Decisions

- Model behavior before modification.
- Validate with representative hardware and media.

## Knowledge Produced

- State machines
- Behavioral contracts
- Validation targets

## Knowledge Consumed

- Interfaces
- Resources
- Services
- Media behavior

## Current Engineering State

Current behavior work includes initialization, command dispatch, authentication, partition switching, media state, tray events, streaming, caching, power, and vendor features.

## Engineering Lessons

- A handler address is not a behavior model.
- Representative media is required to expose representative firmware behavior.

## Negative Knowledge

Project Frankenstein no longer assumes:

- One routine fully explains a capability.
- Emulator success without hardware comparison establishes behavior.

## Current Implementations

- Emulator sessions
- Hardware protocol traces
- Analyzer correlations

## Future Implementations

- Formal behavioral models
- Cross-family behavior comparison

## Open Questions

To be expanded during engineering review.

## Why This Chapter Exists

Capability engineering is possible only after behavior is understood.
