TECH TALK

A journal of bus architecture tips & techniques

Utilizing the Benefits of AdvancedTCA Mezzanine Cards

The AdvancedTCA (ATCA) PICMG 3.x family of standards is the first to be designed for the telecom industry. Although CompactPCI has been adapted to fit some telecom applications, it was designed for the industrial sector. The main focus of ATCA is to provide a basic foundation for all components within a platform allowing for what is known as "RASM" or Reliability, Availability, and Systems Management.

The PICMG Advanced Mezzanine Card (AMC) specification defines base level requirements for a wide range of high-speed mezzanine cards optimized for, but not limited to, ATCA carriers. In addition to ATCA, target interfaces include PCI Express, Advanced Switching, Serial Rapid I/O, and Gigabit Ethernet. ATCA presently is for applications primarily in the access/edge. However, there are a variety of areas within the control plane, user plane, and transport plane in which it makes sense to utilize ATCA modular building blocks to maximize investments. AMCs enable a modular building block design for both industry standard and proprietary carrier boards. The AMC specification opens up larger markets with more unique functions and creates economies of scale that ultimately lowers prices.

The primary functions of AMC modules are field replaceable processor resources, storage, and interfaces such as T1/E1/J1, OC-3 /STM-1, OC-12 /STM-4, Fast Ethernet, and Gigabit Ethernet. All elements must work within the bounds of the PICMG 3.0 base specification and build upon its strengths of Reliability, Availability, and Serviceability (RAS).

Differences between AMC and PMC
Although PCI Mezzanine Card (PMC) modules, common in CompactPCI and VMEbus systems, may have similar line interfaces as AMCs, there are several major differences between the two modules:

• AMCs have more board real estate.
  
  

• AMCs have an agnostic interconnect supporting a variety of high-speed fabrics. A PMC module has one interconnect: the PCI bus.
  
  
• AMCs are hot swappable and front loadable. They minimize downtime and cost for field replacements, thus, supporting availability and serviceability objectives.
  
  
• AMCs are optimized for high speed LVDS interconnects. They have a low pin count thereby reducing the amount of space required on both the AMC and the carrier board, yet providing sufficient real estate for intended interconnects and usage models.
  
  
• AMCs were designed to meet the needs of higher electrical power requirements.

What do we have available today?
Since the AMC specification was ratified in February of 2005, several companies have announced new AMC offerings, and those who have prototypes available have started interoperability testing. The first wave of compliant and fully released AMCs is scheduled to hit the market in the third quarter of this year.

The initial ATCA applications will use today's available PMC mezzanines. This will allow immediate facilitation of ATCA platforms. One of the advantages of using PMCs or PTMCs in ATCA is availability. There are a large variety of readily available products on the market today, many with complete software packages. An example is Interphase's AdvancedTCA Network Processor Blade.

As the ATCA mezzanine standard matures, new mezzanine modules will evolve allowing the market to take advantage of the hot swap capabilities for increased reliability and simplified maintenance, improved performance, and improved support for higher speed interfaces.

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