Industrial automation plays a critical role in the regulated environments of the pharmaceutical industry. The systems SCADA (Supervisory Control and Data Acquisition) and the PLC (Programmable Logic Controllers) They are essential elements for the control, monitoring and data acquisition of critical processes. Due to their impact on product quality, data integrity, and regulatory compliance, these systems must be designed, implemented, and validated following a documented and traceable approach.

Within the validation life cycle based on the modelo V and in the GAMP® 5 recommendationsv (Good Automated Manufacturing Practice), los documentos URS (User Requirements Specification), FS (Functional Specification) y DS (Design Specification) constitute the basis for the development and validation of automated systems.

1. Normative and regulatory framework

SCADA and PLC systems used in GMP environments must comply with various Regulatory requirements and international guidelines, among which stand out:

• EU GMP Annex 11 – Computerised Systems.
• FDA 21 CFR Part 11 – Electronic Records and Electronic Signatures.
• GAMP® 5 Second Edition.
• PIC/S PI-011.
• ISPE Baseline Guide Volume 5.
• Data integrity Guidance (MHRA, FDA, WHO).

The correct preparation of URS, FS and DS allows us to demonstrate that the system has been developed in accordance with requirements previously defined and facilitates traceability during the qualification and validation phases.

2. User Requirements Specification (URS)

The URS (User Requirements Specification) is the document that describes what the user needs of the system without going into technical implementation details.

It represents the starting point of the project and constitutes the main reference for all subsequent design, development, testing and validation activities.

Their goals son:

• Clearly define operational needs.
• Set performance expectations.
• Identify GMP requirements.
• Serve as a basis for evaluating suppliers.
• Allow regulatory traceability.

Typical content of a URS for SCADA and PLC

General information	System name. Range. Description of the process. Affected areas.
Functional requirements	Examples: The system shall automatically control the CIP sequence. The PLC must manage high temperature alarms. The SCADA will allow setpoints to be modified by authorized users.
Data integrity requirements	Audit Trail. User management. Change traceability. · Protection against unauthorized modifications.
Alarm requirements	Alarm classification. Prioritization. Mandatory recognition. Historical record.
Communications requirements	Ethernet/IP. Profinet. Modbus TCP. OPC UA.
Security requirements	Role-based access. Password management. Automatic lock. Backup and recovery.
Reporting requirements	Batch reports. Trending. Data export. Electronic reports.
urs requirement example URS-023: the SCADA system must electronically record all modifications of critical setpoints indicating user, date, time, previous value and new value.

Important: URS do not define technical solutions or determine how requirements will be met.

3. Functional Specification (FS)

The FS (Functional Specification) translates user requirements into specific functions that the system must execute.

Answer the question: How will the system meet the requirements defined in the URS?

FS is usually developed jointly between automation engineering, systems integrator, production users; and quality and validation.

Los goals of this document are:

• Detail the functionalities of the system.
• Define the operational logic.
• Describe interactions between teams.
• Serve as a basis for technical design.

Typical content of a FS

Functional architecture	Description of: PLC. SCADA. Industrial networks. Servers.
Process description	Example: CIP sequence Verification of initial conditions. Automatic opening of valves. Pump start. Temperature control. Completion and generation of report.
User management	Administrator. Supervisor. Operator. Maintenance.
Trends and historicization	Registered variables. Sampling frequency. · Retention time.
Interfaces with other systems	Example: MES. LIMS. ERP. Historians.
FS Requirement Example FS-045: When the temperature reaches 80°C for more than 10 seconds, the PLC will activate alarm ALM-TEMP-001 and automatically close the steam valve.

4. Design Specification (DS)

The DS (Design Specification) describes the detailed technical implementation of the system.

Answer the question: How will the system be built?

It is the document used by programmers and automation engineers to develop software and configure hardware.

Los goals of the DS are:

• Define the technical architecture.
• Document the programming.
• Specify hardware and software.
• Facilitate maintenance and future modifications.

Content of a DS

Hardware Design	PLC Manufacturer. Model. CPU. DB (Data Blocks). Nomenclature Example: AI_TEMP_101 DI_PUMP_RUN AO_SPEED_SET
SCADA design	Servers. Client stations. Redundancy. Virtualization.
Database Design	Historical structure. Alarms. Events. Audit Trail.
HMI Screen Design	Navigation. Colors. Symbology. Alarm management.
Communications Design	Example: PLC ↔ SCADA through OPC UA.
Programming Design	Block Structure FB (Function Blocks). FC (Functions).
DS Requirement Example DS-112: The ALM-TEMP-001 alarm will be programmed within the FB_Alarm_Manager block using a TON timing of 10 seconds and recorded in the Hist_Alarm table.

5. Traceability between URS, FS and DS

One of the most important aspects during validation is maintain a complete traceability matrix. For example:

URS	FS	DS	Test
URS-023	FS-045	DS-112	OQ-008
URS-031	FS-052	DS-145	OQ-015

This traceability allows to demonstrate what:

1. Every user requirement has been designed.
2. Each design has been implemented.
3. Each function has been verified by testing.

6. Relationship with qualification activities

The URS, FS and DS documents directly feed the validation activities:

Document	Use in Validation
URS	Risk assessment and GMP requirements
FS	Development of functional tests
DS	Technical verification
FAT	Pre-shipment confirmation
SAT	Confirmation in plant
IQ	Installation verification
OQ	Functional verification
PQ	Performance verification

7. Good practices for the preparation of URS, FS and DS

URS	Use clear and verifiable language. Avoid technical solutions. Define acceptance criteria.
FS	Fully describe the operating logic. Incorporate flow charts. Identify alarms and exceptions.
DS	Maintain consistency with the FS. Document all programming. Control versions and changes.
For all three documents Apply GMP document management. Maintain bidirectional traceability. Review and formally approve. Integrate risk assessment.

Conclusion

Proper development of specifications URS, FS y DS constitutes the cornerstone for the success of any automation project based on SCADA and PLC within a regulated pharmaceutical environment. These documents allow business needs to be translated into robust technical solutions, guaranteeing complete traceability from user requirements to validation tests.

A solid documentary strategy, aligned with GAMP® 5, Annex 11 and 21 CFR Part 11, not only facilitates regulatory compliance, but also reduces project risks, improves system maintainability and ensures that automated processes operate reliably throughout their life cycle.

The difference between a system that delivers and a system that delivers value begins with a well-defined specification. Contact us to take your automation and validation projects to the next level.