Modern manufacturing facilities demand synchronized processes and seamless communication between equipment and factory host systems. SEMI standards, particularly the SECS/GEM (SEMI Equipment Communications Standard/Generic Equipment Model) suite of standards, have become the backbone of automation in semiconductor manufacturing by standardizing communication protocols between these entities. This article introduces you to the GEM standard, and begins a series of 5 articles that describe the various features and benefits of GEM.
What is the GEM Standard?
GEM refers to a set of SEMI standards that govern the communication between manufacturing equipment and factory host computer systems. The message layer standard, SEMI E5 SECS-II, defines a generic message structure and an extensive library of messages that implement the automation functions shown in Figure 1. (you know the one!) The protocol layer standard, SEMI E37 High-Speed Message Service (HSMS), defines a binary structure to transfer SECS-II messages using TCP/IP. SEMI E30 GEM defines a minimum set of requirements, additional (optional) capabilities, use cases and user scenarios for a subset of SECS-II messages.?
GEM is implemented on an equipment and is used by the factory to access command and control functions. Since it is a mature industry standard, any GEM-compliant host software can communicate with any GEM-compliant equipment. When fully implemented on the equipment, the standards enable factory software to completely control and monitor the equipment by means of its GEM interface. These standards provide numerous benefits to both equipment manufacturers and factories, several of which are highlighted in this and future articles.
Benefits of GEM
- Enhanced Interoperability: GEM enables seamless integration between diverse factory hosts and a large variety of equipment types, regardless of manufacturer.
- Data Transparency: GEM supports real-time monitoring and analytics by transmitting critical data directly from equipment to host systems.
- Reduced Costs: GEM interfaces eliminate the need for custom integration solutions, significantly reducing engineering costs for both factories and equipment manufacturers.
- Scalability: From simple devices to highly complex equipment, GEM adapts to suit varying levels of complexity.
- Broad Industry Support: GEM is widely adopted across several high-tech manufacturing industries such as semiconductors, photovoltaic cells, PCBs, FPDs, and more.
Introducing the GEM Control State Model
The GEM Control State Model is an important component of GEM’s operational framework. It governs the level of cooperation between the host system and equipment, defining the interactions at differentiated control levels. This systematic approach prevents conflicts, ensuring that only authorized entities can command and control the equipment at any time.
There are three primary control levels in the GEM Control State Model, each specifying the distinct privileges and restrictions for host system and operator interactions: Remote Control, Local Control and Offline Control.
Remote Control
Remote control functionality ensures that host control is paramount, enabling the host to oversee and command equipment operations entirely. On-site operator interaction with the equipment is minimal and strictly limited based on configuration settings. Key commands such as START, STOP, and PAUSE are issued remotely from the host using GEM Remote Commands to effect precise equipment control.
Local Control
Under local control, the operator retains primary control of the equipment, ensuring the ability to override host commands if necessary for safety or operational reasons. The host can gather information such as status readings, trace data, and event notifications but lacks the ability to execute critical commands affecting active equipment processes. Restrictions are in place during local control to prevent hosts from initiating physical operations, including starting or stopping jobs.
Offline Control
Under offline control, operators have complete control while host systems are effectively locked out of operations. Host capabilities are highly restricted, limited primarily to establishing basic communication or transitioning back to an online state when the operator initiates it.
The separation of these control levels ensures operational safety and avoids conflicts that could cause harm to plant, product, or personnel.
How the Control State Model Operates
A core feature of the GEM Control State Model is its state machine, which governs how the system transitions between control levels.
- Operator Governance: Operators have superior control over state transitions to safeguard on-site actions and ensure operational safety. While the host can request changes in control states, the final decision often lies with the operator.
- State Display and Control: Equipment must always display the current control state to operators. Clearly visible control state displays are fundamental to informing on-site users of the equipment’s operational status.
- Control Switch Implementation: The equipment must include physical or software-based switches to transition between control levels. These switches may involve hardware buttons or persistently stored software configurations for long-term operation settings.
- Conditional Transitions: Some state transitions, like moving from Host Offline to Online, can be conditional and configured based on a particular set of predefined equipment settings.
For factories reliant on high precision and clear operational authority, this model offers a robust framework adaptable to diverse production scenarios.
So what are the key benefits of the GEM Control State Model?
Conflict Resolution
The framework eliminates ambiguity by clearly determining which entity (host or operator) has control at every moment. This protects against operational conflicts that could arise from simultaneous command inputs.
Enhanced Safety
By prioritizing local operator control, the model allows for rapid interventions in case of emergency or unsafe operations.
Operational Efficiency
Hosts can predefine control and communication parameters, streamlining command flow and reducing setup times.
Flexibility and Customization
With switch-based transitions and configurable conditional states, manufacturers can tailor the Control State Model based on equipment-specific or factory-level operational requirements.
A Critical Aspect of Smart Manufacturing
The GEM Control State Model strengthens manufacturing automation by balancing the power between operators and host systems while maintaining efficient operations. Beyond this, it forms the foundation required for implementing higher-order smart manufacturing standards, such as the automation concepts in the GEM300 family of standards.
Moving Forward with GEM
For factories seeking scalable, cost-efficient, and adaptable solutions for equipment communication and control, the GEM standard is a clear choice. Whether you’re venturing into automated manufacturing or upgrading legacy systems, implementing GEM ensures that your operations remain efficient, secure, and ready for the challenges of tomorrow.