The hardware platform management functions in AdvancedTCA and MicroTCA systems can greatly benefit from the use of mixed-signal FPGAs.

One of the most exciting aspects of AdvancedTCA and MicroTCA is that these technologies are now starting to be deployed in a wide variety of different market segments, ranging from industrial to medical to military applications. One result of this is that a large number of system architects, hardware design engineers, and software developers now have to “ramp up” their knowledge of these technologies.

A Little History

In order to make sure that we’re all tap-dancing to the same drum beat, let’s start with a little history. The Advanced Telecommunications Computing Architecture (ATCA or AdvancedTCA) was originally conceived for use in “carrier grade” communications equipment.

The need for such an architecture was first identified circa 2000. Under the auspices of the PCI Industrial Computer Manufacturers Group (PICMG), with more than 100 companies participating, the initial AdvancedTCA specification (officially known as PICMG3.0) was drafted in 2002. The first AdvancedTCA products were introduced circa 2004, and volume deployment commenced around 2006.

The term Advanced Mezzanine Card (AMC or AdvancedMC) refers to a printed circuit board (PCB) that follows a certain set of PICMG specifications and that is designed to work on any AdvancedTCA carrier card. In order to reduce costs for certain applications, the MicroTCA (MTCA or µTCA) specification was ratified in July 2006. This allows AMC modules to be plugged directly into a backplane, thereby providing a more affordable solution for cost-sensitive applications.

Indeed, the MicroTCA standard enables commercial-of-the-shelf (COTS) chassis applications for which the AMC cards can function without the need for an AdvancedTCA carrier card, according to a representative from Performance Technologies, Inc. (www.pt.com) In such cases, the functions of the ATCA carrier board and of the ATCA shelf manager are concentrated on one board, which is called the MicroTCA Carrier Hub (MCH). Several companies provide AMC and MCH products, including Performance Technologies recent announced that its IPnexus MicroTCA systems now support an AdvancedMC option featuring the Intel® EP80579 x-86 based integrated processor.
A key feature of AdvancedTCA- and MicroTCA-based systems – which may be referred to collectively as xTCA – is that they offer improved Reliability, Availability and Serviceability (RAS). In this context, Reliability refers to the ability to detect and correct system faults such as corruption to the data being processed; in a worst case scenario, the portion of the system that is seeing corruption should report any problems to a higher-level authority and gracefully shutdown its operations.

Availability refers to the amount of time a system is actually operating as a percentage of the total time it should be operating. For example, a system designed to provide an availability of 99.9999% (known as “six nines”) would mean that this system would have a downtime of only 31.5 seconds a year.

Serviceability refers to the ability to easily detect, isolate, and diagnose any problems as they arise. There are many aspects to this, such as automatically monitoring system characteristics such as voltages, currents, and temperatures; automatically reporting any problems to a “higher authority”; and allowing repairs to be made with as little disruption to normal operations as possible.

With regard to this latter point, one aspect of serviceability is the ability to “hot swap” AMC modules and/or AdvancedTCA carrier cards. In order to facilitate this, these modules and cards have connectors that support traces with different lengths. This means designers know which traces will become active in which order when a module or card is inserted into the system (also which traces will become inactive in which order when a module or card is removed from the system).

Hardware Platform Management

A very important facet of xTCA-based systems is that all cards, modules, and enclosures have a layer that performs hardware platform management (also known as “shelf management”). Based on the Intelligent Platform Management Interface (IPMI), this hardware platform management infrastructure is a key enabler for the stringent availability and serviceability requirements.

One aspect of this is the fact that each card, module, and enclosure includes machine-accessible inventory data such as types, versions, revisions, and serial numbers. This facilitates tracking boards as they enter and leave the system and ensuring their compatibility with other elements in the system.

Another aspect involves such things as power sequence management (powering various devices and functions up and down in defined sequences), voltage, current, and temperature monitoring at multiple points on each board, cooling management functions, high-speed communication management, and so forth.

All of this is mandatory. Every card or module has a local controller on-board; also every chassis or shelf has a controller that collects all of this data and presents it to higher-level management systems as required.

Implementing all of this is non-trivial. The IPMI specification itself is over 400 pages long, and there are hundreds more pages associated with the management portions of the xTCA and AMC specifications. In the early days of xTCA, it was not uncommon for the designers of these systems to undertake all aspects of the design, including the hardware platform management functions. Today, however, there is an increasing trend for developers of xTCA products to employ third-party platform management building blocks. This allows them to focus their resources on their unique, differentiating, and value-add features.

µPs, µCs, and Mixed-Signal FPGAs (Oh My!)

The original shelf management solutions were typically based on off-the-shelf microprocessors and microcontrollers. One company that specializes in creating xTCA management building blocks for use by other developers is Pigeon Point Systems (www.pigeonpoint.com). As Robert Pettigrew, Director of ATCA product marketing at Emerson Network Power Embedded computing says: “Pigeon Point’s solutions are the de facto standard for shelf management functions.”

Initially, Pigeon Point’s platform management modules were based on fixed-function microcontrollers such as the H8S from Renesas or the AVR from Atmel. However, although such microcontrollers can be extremely useful, they are typically limited to around eight or so analog inputs. Also, whatever was designed into these devices several years ago is all that’s there. If additional functionality is required, it has to be “bolted on” in the form of additional devices.

An alternative solution is to employ mixed-signal FPGAs such as the Fusion family from Actel (www.actel.com). (In fact, there is so much synergy between Actel’s mixed-signal FPGAs and Pigeon Point’s xTCA shelf management modules that Actel recently acquired Pigeon Point.) Fusion FPGAs are flash-based devices, so they consume very little power and they are live at power up. In turn, this means that they can be used for power-sequencing operations like controlling the order in which other devices on the board are powered-up.

Of particular interest with regard to monitoring voltage, current, and temperature values is the fact that Fusion FPGAs support up to 30 analog inputs coupled with a mixture of programmable analog fabric and programmable digital fabric. Among other things, the programmable analog fabric can contain configurable pre-scaler functions and a configurable analog-to-digital converter that can be programmed to support different sample rates and resolutions.

Furthermore, in addition to configuring some of the digital fabric to perform various acceleration functions, designers can also add one or more soft CPU cores, which can be used to monitor the signals coming from the programmable analog fabric and to make decisions based on these values.

So, in conclusion, if you are new to xTCA and have been tasked with developing systems using this technology, when it comes to the shelf management portions of your designs, you can either create these from the ground up, or you can take advantage of existing solutions from third-party vendors. And whichever way you decide to go, you should certainly consider a solution based on a mixed-signal FPGA, as opposed to a fixed-function microcontroller.

Clive (Max) Maxfield is author of Bebop to the Boolean Boogie (An Unconventional Guide to Electronics) and The Design Warrior’s Guide to FPGAs (Devices, Tools, and Flows). Max also is the co-author of How Computers Do Math, featuring the pedagogical and phantasmagorical virtual DIY Calculator
(www.DIYCalculator.com).