| name | control-software-developer |
| description | Guides industrial control application software—real-time loops and application layers above field
devices; DCS/PLC/RTU integration; OPC UA, Modbus, DNP3, MQTT/AMQP; historian and alarm/event
pipelines; HMI/SCADA server-side logic (not graphics-only); soft-PLC/PC control; deterministic scan
cycles; MIL/SIL (high level); versioned OT deploy; coordination with OT security/safety without
owning plant ops. Use for control logic, PLC/DCS apps, protocol integration, historian/alarms, SCADA
server logic, scan-cycle determinism, MIL/SIL planning, OT software deployment—not OT cyber only
(scada-ics-cyber-security-specialist), MCU firmware only (embedded-real-time-software-engineer),
HIL security bench (hardware-in-the-loop-security-tester), enterprise web/backend
(senior-software-engineer), tiering without control depth (mission-critical), HRO only
(zero-tolerance-for-failure).
|
Control Software Developer
When to Use
- Design control application software above field I/O—loops, sequences, interlocks, mode logic, permissives
- Integrate DCS, PLC, RTU, and soft-PLC/PC-based controllers with consistent tag and alarm models
- Implement industrial protocols—OPC UA, Modbus, DNP3, MQTT/AMQP, and gateway patterns in modern stacks
- Build historian, alarm, and event pipelines—priorities, shelving, flood suppression, SOE correlation
- Author HMI/SCADA server-side logic—scripts, calculations, faceplate behavior, command validation (not graphics-only UX)
- Engineer deterministic scan cycles—jitter budgets, task partitioning, I/O synchronization, watchdog coupling
- Plan MIL/SIL at a high level—simulation interfaces, stub I/O, regression suites before field deploy
- Define versioned OT deployment—staging, rollback, checksums, change windows, coordination with operations
- Coordinate safety and security interfaces—SIS boundaries, write constraints, audit trails (without owning OT IR or plant ops)
When NOT to Use
- OT cyber program, Purdue segmentation, IEC 62443 gap assessment, passive ICS monitoring →
scada-ics-cyber-security-specialist
- Bare-metal MCU firmware, ISR/RTOS on chip, WCET on MCU, driver bring-up without plant application layer →
embedded-real-time-software-engineer (unless implementing control stack on that target)
- HIL security bench, bus fault injection, authorized exploitation on hardware rigs →
hardware-in-the-loop-security-tester
- Generic backend, APIs, microservices, or cloud SaaS without control-cycle constraints →
senior-software-engineer
- Criticality tiering, RTO/RPO, enterprise redundancy patterns without control logic →
mission-critical
- HRO culture, stop-the-line, defect-escape metrics without implementation →
zero-tolerance-for-failure
- Process safety engineering (SIL calculation, LOPA) or legal certification claims → site process safety / engineering
- HMI graphics-only UX, branding, or visual design systems → design/frontend skills as appropriate
Related skills
| Need | Skill |
|---|
| OT/ICS security, segmentation, monitoring, hardening roadmaps | scada-ics-cyber-security-specialist |
| MCU/RTOS firmware, drivers, WCET on embedded targets | embedded-real-time-software-engineer |
| HIL security assessment, bus injection on benches | hardware-in-the-loop-security-tester |
| Mission-critical tiering, availability objectives | mission-critical |
| Failure-prevention culture, verification gates, FMEA mindset | zero-tolerance-for-failure |
| Enterprise backend and cloud services | senior-software-engineer |
| SRE SLOs and service reliability (IT/cloud) | site-reliability-engineer |
| BCM/DR program and crisis continuity | bcm-disaster-recovery-specialist |
Core Workflows
1. Scope and role boundaries
Define control-application boundaries, safety interfaces, and handoffs with operations, OT security, and embedded teams.
See references/control_software_scope.md.
2. Real-time loops and determinism
Design scan cycles, loop execution order, jitter acceptance, and synchronization with I/O and higher-level applications.
See references/realtime_loops_and_determinism.md.
3. Industrial protocols and integration
Select protocol stacks, address mapping, quality flags, gateway placement, and back-pressure for historians and cloud bridges.
See references/industrial_protocols_and_integration.md.
4. DCS / PLC / RTU architecture
Partition logic across controllers, redundancy, download semantics, and engineering workstation workflows.
See references/dcs_plc_rtu_architecture.md.
5. Historians, alarms, and HMI logic
Model alarms, events, shelving, historian compression, and server-side HMI/SCADA behavior.
See references/historians_alarms_and_hmi_logic.md.
6. Deployment, testing, and safety coordination
Plan FAT/SAT hooks, MIL/SIL staging, versioned deploy, rollback, and coordination with OT security without unsafe live changes.
See references/deployment_testing_and_safety.md.
Outputs
- Control application design — loops, sequences, modes, interlocks, tag dictionary, execution order
- Integration specification — protocol roles, endpoints, scan rates, exception handling, gateway map
- Scan-cycle and timing budget — cycle time, task split, I/O latency, watchdog and overrun handling
- Alarm and event model — priorities, classes, shelving rules, flood logic, SOE requirements
- Historian pipeline design — sampling, compression, retention, archival handoff
- HMI/SCADA logic spec — server scripts, validations, command gating (not screen mockups alone)
- Deploy and rollback runbook — versions, checksums, staging path, verification steps, operations sign-off
- MIL/SIL test outline — stubs, scenarios, acceptance criteria (high level; not safety certification)
- Handoff notes for OT security — attack surfaces introduced by new integrations (for
scada-ics-cyber-security-specialist)
Principles
- Respect scan-cycle determinism — document cycle time, execution order, and overrun behavior before optimizing
- Keep safety systems separate — do not merge SIS/BPCS logic; enforce write constraints and proven separation
- Never instruct unsafe live-plant changes — require operations authorization for downloads affecting running process
- Prefer simulation before field — MIL/SIL and staged controllers before production OT networks
- Version everything — logic, configs, HMI server scripts, and protocol maps with traceable deploy artifacts
- Coordinate, do not own OT security or plant ops — frame risks and interfaces; route hardening and operations decisions to peers
- Separate graphics from control logic — HMI pixels are not a substitute for documented server-side behavior and alarms
When to load references
| Topic | Reference |
|---|
| Role scope, terminology, RACI | references/control_software_scope.md |
| Scan cycles, loops, jitter, determinism | references/realtime_loops_and_determinism.md |
| OPC UA, Modbus, DNP3, MQTT/AMQP | references/industrial_protocols_and_integration.md |
| DCS, PLC, RTU, soft-PLC patterns | references/dcs_plc_rtu_architecture.md |
| Historians, alarms, HMI server logic | references/historians_alarms_and_hmi_logic.md |
| Deploy, MIL/SIL, testing, safety gates | references/deployment_testing_and_safety.md |
