InterEdge - PICMG

Family of Specifications

InterEdge is an open modular architecture for process control systems (PCS). It consists of Compute Modules, Switch Modules, I/O Modules, Power Supply Modules, and their associated interconnecting bus communication protocols and data models.

InterEdge enables multi-vendor hardware interoperability and interchangeability along with system management and hot-swapping capabilities that ensure high availability. This approach provides end-users with the benefits of large-scale hardware commonality and state-of-the-art computational resources while reducing the costs of integration, maintenance, and upgrades.

The Benefit of a Modular Standard for the Process Industry

InterEdge is intended for broad process industry use as an alternative to Industrial PCs (IPC), Programmable Logic Controllers (PLC), Distributed Control Systems (DCS) and their associated I/O modules. With its modular architecture, InterEdge can consolidate the functions of all of these systems into a single platform. This common platform can then be employed across a wide range of process industries including refining, chemical, oil and gas, pharmaceuticals, metals and mining, pulp and paper, and food and beverage.

By replacing proprietary edge devices such as PLCs with an open, modular architecture, industrial organizations can avoid the many economic penalties associated with vendor lock-in. For example, if faced with obsolescence or a need for more computational horsepower and/or security, an online “rip & replace” imposes a significant switching cost. As such, these edge components remain in place for decades with static functional capabilities.

In contrast, the standardization of InterEdge Modules allow online upgrades and/or replacements while the plant is running. This hardware component interchangeability translates into value by allowing manufacturers to improve their competitive position through emerging trends in digitization, Industrial IoT, and Industry 4.0.

InterEdge Module and Bus Basics

InterEdge is centered around creating a standardized, modular, and robust architecture for pluggable systems.

InterEdge is a modular, pluggable system for process control and automation. The architecture is designed to be flexible, allowing for widely varying implementations while ensuring interoperability. The specification centers on three types of Modules:

I/O Modules handle the interface functionality for field devices like sensors and actuaries.
Switch Modules are responsible for network switching within a localized InterEdge setup.
Compute Modules function as a gateway to higher-level control networks and perform regulatory functions for Process Control Systems (PCS), using standards like IEC 61499 and IEC 61131

InterEdge Modules are interconnected through data and power buses housed in a PCB backplanes:

Compute Module Data Bus (CMDB): A dual 1000BASE-KX network connecting Compute Modules to the PCS control network, with a System Management Network layered on top for management functionality.
Compute Module Power Bus (CMPB): Distributes power to Compute Modules.
I/O Module Data Bus (IOMDB): Connects Compute Modules to I/O Modules, consisting of a primary dual CAN FD bus and a secondary, reserved dual single-pair Ethernet bus.
I/O Module Power Bus (IOMPB): Distributes power to I/O Modules.
I/O Module Termination Assembly (TA) Interface: Standardizes field signal interfaces at the I/O Module backplane connector.

The entire InterEdge system is in turn connected to an external Control Network, typically a 1000BASE-T switched network implemented within the process control facility.

Physical and Mechanical Characteristics of InterEdge

InterEdge specifies Module dimensions, physical interfaces, and mounting details to ensure compatibility and performance. Compute and Switch Modules must be 35 mm wide, 215 mm tall, and between 120-200 mm deep. Single-Channel I/O Modules are 14 mm wide, 90 mm tall, and between 55-70 mm deep. Multi-Chanel I/O Modules will be included in a future revision of the specification.

All Modules are mounted within cradles. For Compute and Switch Modules these cradles must be at least 55 mm wide, 250 mm tall, and between 108 mm deep. Single-Channel I/O Modules are a minimum of 20 mm wide, 105 mm tall, and 38 mm deep.

Compute and Switch Modules must be mounted with a minimum pitch of 65 mm, leaving a keepout zone between Modules for airflow. Single-Channel I/O Modules have a minimum mounting pitch of 19 mm, meaning that once the width of the cradle is accounted for, no keepout zone is required between these Modules

Other requirements include:

Polarization feature: Ensures that only a specific Module type can be inserted in the correct orientation, preventing improper installation.
Module Insertion Stop Interface: Ensures that the Module is inserted at the correct depth
Latching with two positions: Supports a fully-inserted position that connects the Module to the backplane and a “parked” position that holds the Module in place while being electrically isolated from the backplane.
Sufficient latching force: Ensures a secure installation and resistant to mechanical stresses such as vibration.
Easy removal: Modules must be graspable at the center of the front and preferably removable with a single hand.

These requirements aim to ensure proper Module insertion and operation within the InterEdge framework.

InterEdge Module Pinout Overview

InterEdge details pinouts for each of the three Module types. It also provides electrical requirements for features including hot-plugging and anti-tamper measures:

Hot-Plugging: Modules must support hot-plugging, with connectors designed to prevent electrical overstress during insertion/extraction.
Anti-Tamper Requirements: Modules must connect to two anti-tamper contacts; details on functionality will be defined in future standards.
Module Addressing: Modules should receive a unique address via the rear plugin connector, with specific signaling levels for address bit inputs and odd parity for the address parity bit.
Data Bus Requirements: Modules using the 1000BASE-KX CMDB must implement specified interfaces and comply with IEEE 802.3 Clause 70, including providing AC coupling capacitors on all implemented receive pairs of 1000BASE-KX ports with specific capacitance values and tolerances.

InterEdge Power Buses

InterEdge utilizes three distinct power buses:

24VDC Power Supply: The system should use a 24VDC power supply with pluggable connectors or direct-wire interfaces, within a tolerance of +5/-10%.
Compute Module Power Bus (CMPB): This should be a redundant power bus capable of supplying 30W at 24VDC to each Compute and Switch Module slot, with overcurrent and short-circuit protection recommended.
I/O Module Power Bus (IOMPB): This bus should be capable of supplying 3W at 24VDC to each I/O Module slot, with separate routing for a 24VDC Field Interface that can provide up to 0.5A to a Single-Channel I/O Module slot. Overcurrent and short-circuit protection are also recommended for this bus.

These requirements ensure that the power distribution within the InterEdge system is robust, reliable, and can cater to the power needs of various Modules while protecting the system from power-related issues.

Using InterEdge with the O-PAS Standard from the Open Process Automation Forum (OPAF)

InterEdge originated as part of the O-PAF Standard from the Open Process Automation Forum (OPAF), which is part of The Open Group. Consisting of 110+ members, this organization is dedicated to creating an interoperable architecture for industrial process automation, using existing standards wherever possible. Known as O-PAS, this “standard of standards” is supported by the leading forces in process automation including system suppliers, engineering firms, governmental bodies, research institutions, and end customers.

Now maintained by PICMG, InterEdge integrates with the broader O-PAS effort to enable solutions that are interoperable across various vendors and platforms. Key benefits include:

Modularity and Interoperability: InterEdge Modules support O-PAS interoperability specifications, ensuring that the Modules work seamlessly within an O-PAS compliant ecosystem.

Standardized Communication: Alignment with the protocols endorsed by O-PAS enables seamless data exchange and integration within the broader process control architecture.
Robustness and Security: By integrating O-PAS security standards, InterEdge systems are resistant to cyber threats.
Configuration and System Management: The modular nature of InterEdge, combined with the configuration and system management tools provided by O-PAS compliant systems, enables a highly flexible and manageable process control system. This simplifies the deployment, monitoring, and maintenance of complex industrial systems.
Future-Proofing and Scalability: By integrating InterEdge’s modular architecture with the O-PAS Standard’s open architecture, organizations can create systems that are not only flexible but also capable of integrating future technological advancements.

Although InterEdge is not directly related to other PICMG standards such as CompactPCI and MicroTCA, it shares their main goal of multi-vendor interoperability for industrial computing. A key differentiator for InterEdge is that it focuses on pluggable Modules rather than on board-level interoperability.

Note that InterEdge does not supplant any existing PICMG specifications. Instead, InterEdge complements these specifications with its unique support for module replacements or upgrades without disconnecting power or interface cabling from the backplane. Existing PICMG do not support this level of modularity and live-power upgradability needed by the process industry.

InterEdge Overview