MRAM extends HMI functionality

HMI capabilities exceed traditional visualization, so Siemens incorporated MRAM into its newest HMIs to maintain software-programmable logic controller process data without the need for battery-backup.
By Control Engineering Staff June 13, 2008

One of the latest innovations in the area of memory is magnetoresistive random access memory, MRAM , which uses electron spin to store information. MRAM has the potential to combine the density of dynamic RAM ( DRAM ) with the speed of static RAM ( SRAM ) and non-volatility of Flash memory or hard disk, while consuming a very low amount of power. MRAM can resist high radiation and can operate in extreme temperature conditions. These features make it advantageous to incorporate this technology into the design of the HMI.
Siemens has incorporated MRAM into its newest human-machine interfaces ( HMIs ), the MP277 and MP377, which are available in touch screen and keypad versions. Screen sizes start at 8 in. and go up to 19 in.
Because HMI capabilities now go beyond traditional visualization; applications that can be run on the multipanels include data collection and control. The MP277 and MP377’s MRAM provides an easy-to-use, non-volatile memory that maintains software-programmable logic controller process data for its HMI platforms without the need for battery-backup.
For the purposes of this article, the focus will be on the industrial automation market and the individuals who operate equipment. In the industrial automation market, the terminology HMI originally referred to the operator interface, operator panels and human machine interface. Today, HMI’s are in every type of application, from low end visualization to high end distributed control systems.
Just as the naming convention has evolved, so has the technology that is being incorporated into the devices. Initially, HMI’s were developed as a way to replace pilot devices (such as lights and push buttons) in a panel to give access to data areas in the PLC. Now, the HMI has become an integral part of the automation solution and has evolved beyond visualization to serve applications that once were reserved for PC’s. Touch screen technology, operating systems, communications and memory are all areas where there have been drastic enhancements. These improvements and convergence of the technologies have made the HMI an integration platform.
A critical component in the design of the HMI is memory, which is used in a variety of ways. Operating systems rely on memory for the hosting of the core functions. Dedicated operating systems typically use less memory and take up less overhead, but restrict the openness of the system. An embedded operating system, such as Microsoft Windows CE, uses more memory and typically takes up more overhead, but provides more openness and access to modifications.
Development software is used to customize the application by the user/OEM for a specific function, providing a unique graphical interface for the operator. The numbers of screens that can be created depend on the amount of memory allocated for that function. Other components include alarming, messaging and data collection, which enable the archiving of data and rely on memory for the storage of this information.
The controller option enables the implementation of an expandable machine control system in a small form factor that will help reduce overall system cost. The multipanels enable the integration of several automation tasks (visualization, control, data collection, and communication) on a single platform. The control logic uses programming identical to the S7 PLCs making it truly interoperable.
Other expansions to traditional HMI functions are SmartAccess and SmartService. The SmartAccess option makes available simple client/server architectures thus building the basis for innovative design concepts in HMI and automation tasks. For instance, local operator stations can now have plant-wide access to variables or local control room solutions can now have with options for central archiving, analysis and further processing of data.
The SmartService option enables remote control, diagnostics and maintenance via the web browser as well as remote control of an on-site station and maintenance functions (such as downloading projects or downloading/uploading recipes) across the Internet. Troubleshooting operator stations using ready-made diagnostic functions increase visibility, which leads to more uptime.
These software options create a demand for increased non-volatile RAM capacity. The activity they support increases the demand for RAM able to survive a large number of read/write operations while protecting stored data from loss in the event of unexpected power loss. Being a non-volatile RAM capable of undergoing effectively unlimited read/write operations MRAM is the best choice for this application.
Jay Coughlin, manager HMI business USA, Siemens Energy & Automation
Edited by C.G. Masi , senior editor
Control Engineering
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