Taking AdvancedTCA to the Next Level: From Development Units to System Management Solutions Now that the PICMG 3.0 core specification for AdvancedTCA has been ratified and some of the sub-specifications are near finalization, what is the next step for AdvancedTCA? There are three main upcoming developments for ATCA that we will discuss in this article. The first is the design of prototyping systems, which designers will need to develop ATCA-based products effectively. Further, manufacturers will need to take ATCA chassis from the 12U vertical option to various sizes and configurations, including horizontal rackmount chassis. Finally, as the PICMG 3.0 specification is geared towards high-performance central office applications, the system management for ATCA will need to be incorporated. Development Systems Initial AdvancedTCA chassis developments were standardly in a 12U high form format and included 14-slot backplanes in either Dual Star or Mesh configurations. This is a strong solution that offers maximum performance in 19" rackmount applications. However, this much functionality may not be needed for those who want to go through prototyping and development of ATCA products. For prototyping, smaller (and less expensive) chassis, such as a 2U or 3U horizontal unit with 2 backplane slots, may be all that one needs. A 2-slot backplane allows the testing of ATCA switch and line cards in one of the simplest and least costly version possible. The 2-slot backplane is approximately 5U high by 75mm wide. With less PCB layers, it is a cost-effective way to do development work. The 2U/3U chassis would have similar design functions as other sizes. A 3U version would provide more airflow in the system, but some customers may be willing to make sacrifices in order to use the smaller 2U system. Standard configuration design The standard system depicted in the specification consists of a 19" enclosure, 12U (532.55mm) high, accepting fourteen front and I/O boards. The shelf management modules can be mounted in an empty slot or in the I/O area. The high heat dissipation of up to 200W per board can be resolved with six axial fans solution with a maximum airflow of 190 CFM each. In this design, the fans are mounted into the shelf by three pluggable fan trays. Each fan tray can be exchanged independently and has a removable air filter. A plenum between the fans and the boards distributes the front-to-back airflow evenly among the slots. The essential mechanical features are defined in section 2 of the PICMG 3.0 specification. The overall and interface dimensions of the shelf are compliant to ANSI/EIA 310-D section 1, IEC 60297-1 and IEC60297-2. New configuration design Some ATCA systems will require enhanced airflow, and as mentioned above, more powerful system management modules will often be desired. To resolve these issues, a 13U (577mm) high solution can be incorporated. The only difference from the 13U and the 12U high shelf is an extra 1U in space (44.45mm) above the card cage. The additional space accommodates two shelf management modules and enhances airflow. As stated earlier, a 14-slot 12U high unit may be overkill in some applications. The use of smaller stackable chassis in scalable rackmount applications is a popular solution for CompactPCI and other architectures. Therefore, low-profile 4U high systems (176.95mm) have been developed to provide an intermediary solution. Most 4U chassis will accept five front boards and five I/O boards in a horizontal orientation. To facilitate increased shelf manager performance, a Shelf Management Module (SMM) is located above the boards, separated by a divider plate. A 5-slot backplane fits inside the unit. For the backplane, a Replicated Mesh offers the most versatility possible. Dual Star, Mesh, or Replicated Mesh configurations can be utilized within the same backplane. "Replicated" simply means that the Mesh configuration is duplicated, so a redundant set of connections are available. Per the specification, a 5-slot Mesh allows a simple Dual Star to be implemented as the routing from logical slots 1 and 2 for a Mesh has the same connections as routing from a Dual Star. This backplane also has special options. It has a 4-pin header for wiring connections to system management modules (discussed later in the article). For chassis-to-chassis interconnection options, the backplane can incorporate two optional RJ45 connectors to support ICMB (Intelligent Chassis Management Bus). Cooling is an important consideration in a horizontal unit. For the 4U ATCA chassis, a solution with two fans with a maximum airflow of 190 CFM each provides sufficient cooling to the boards. They dissipate up to 1000 watts. The airflow in this configuration is cross-wise right to left. For serviceability, the filter tray and fan tray is separately removable. All AdvancedTCA shelves are designed to accommodate the alignment and safety ground pins located on the front faceplate. Elma Electronic has developed an unique design of the receptacle (patent pending), which provides secure grounding, accurate alignment and accepts wide tolerances of the alignment pin spacing. More information will be provided on this receptacle at a later date. Also, a cable tray can be mounted as an option to the shelf below the boards on the front and rear side. Special Design Considerations Although the specification calls out for stamped sheet metal, incorporating modularity into ATCA designs will be important to offer the industry flexible solutions. Sheet metal solutions are ideal for high volumes, where the economies of scale make them viable. But what about prototype units in new configurations? The costs of stamping and forming for the many design options that customers will no doubt require would be high, and adversely affecting one of the key purposes of ATCA - to keep costs low. Chassis that incorporate modularity will allow the cost-effective implementation of many new solutions. Such a modular approach would be the use of 2mm formed sheet aluminum side plates rigidly held together by four corner extrusions that lend structural integrity and modularity to the chassis. Using mechanical keying features in the interconnection points, the card cage is integrated into the chassis facilitating easy and fast assembly. ESD and EMI control are important issues. The use of formed sheet metal card guides (compliant to PICMG 3.0) into the frame incorporates an innovative approach for the relief of ESD from the front panel. Also, ESD jacks can be located in the front and back of the chassis. Further, chassis shielding is accomplished with the combination of stamped metal EMC contact points and EMC contact strips. For convenience, removable 19" rack flanges can be provided. Standardly located in the front of the chassis, they can be optionally installed in the middle or back of the chassis with convenient allotments for their placement. System Management In order to achieve as close to 100% uptime as possible, a system manager needs to perform several functions. The system manager needs to allow for the monitoring of various peripheral cards as well as power supplies (input voltage, output voltages and temperature), fan speed, temperature at various locations within the chassis and airflow. The system manager should have the capability to adjust the speed of the fans depending on the temperature within the chassis as well as sending out remote alarms via RS232 or 10/100 Ethernet. Today's basic shelf management does basic monitoring of voltages, fans, and temperature. However, they generally do not have controlling functions and do not monitor the actual boards in the system. A new system management module has been created to accomplish these tasks. In cooperation with Pigeon Point Systems, Elma Electronic has developed the Elma IPM Sentry (TM) shelf manager. This module is a flexible platform for shelf and chassis management using the Intelligent Platform Management Interface (IPMI). The shelf manager has been developed for the new PICMG 3.x specifications. However, it is also designed to be easily adapted for PICMG 2.0/2.16/2.17 specification families. The system manager maintains a System Event Log (SEL) along with a Sensor Data Record (SDR), which can be accessed by the IPM controller. The system manager also collects information on the Field Replaceable Units (FRU), such as hot swap peripheral boards. It can read the tachometer input for up to eight fans, using a PWM output to control the fan speed. There are several digital I/O's, input for a Master-only I²C bus as well as a dual IPMB buffered by LTC-4300 for hot insertion and removal onto a live backplane. The Elma IPM Sentry shelf manager will also have the capability of Electronic Keying as stated in the new PICMG 3.x specification. This will eliminate the need for mechanical keys by preventing an improperly placed board from initializing. Further, the shelf manager is programmed to know the topology of the backplane (Dual Star, Mesh, etc.) and know which slots are fabric slots and which are node slots. When a board is plugged into the system, the shelf manager reads the boards, detecting its identity. If the board is incompatible with the slot its plugged into, the shelf manager will not allow the board to initialize. (The board also needs to have the capability to report its identity through the IPMB. PICMG 3.0 defines this board parameter.) The Elma IPM Sentry will be based on a 3U x 160mm or 6U x 80mm form factor carrier card. This will help enable use in both the ATCA and cPCI system environments. As mentioned above, some future AdvancedTCA backplane solutions like the 5-slot Mesh version, will include connector options for connecting to these shelf managers. One solution incorporates a 4-pin header for connection to the three signal lines required on the IPM Sentry. Other options may include direct backplane plugging, depending on the needs of the user. The near future We are already starting to see development units and new configurations for AdvancedTCA systems. Designers will be able to test and prototype with smaller, more basic, and more cost-effective systems. Prototypes have been developed for the IPM Sentry shelf manager, and standard products will be available soon. New horizontal units will offer the industry more choices with different price point options. To help achieve High Availability, system management will take a lead role in maintaining maximum uptime. New System Management Modules will likely be more common in high-end CompactPCI and ATCA systems. Overall, the ATCA landscape will expand with a wider offering for the industry. With more vendors, more widely available products, and more solutions, the strong interest in ATCA may become much stronger. We'll be ready. TM - IPM Sentry is a trademark of Pigeon Point Systems Gary Hanson |
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