Abstract: This paper mainly discusses the advantages of the EVOC-EPI bus compared to the original PICMG1.0 bus specification in the field of industrial computers. The analysis focuses on three aspects: bus scalability, structural stability, and system reliability.
Keywords: EVOC-EPI bus industrial computer reliability
1. Introduction
Industrial control computers are the core of industrial automation equipment and information industry infrastructure. Traditionally, computers used for measurement, control, and management in industrial production processes were collectively referred to as industrial control computers, including the computer itself and process input/output channels. However, today's industrial control computers encompass much more than this, and their applications extend far beyond industrial process control. Therefore, industrial control computers are "rugged computers applied in various fields of national economic development and national defense construction, possessing the ability to adapt to harsh environments and operate stably for extended periods," abbreviated as "industrial control computers."
2. Origin of PICMG PIC/ISA bus IPC industrial control computer
The development of industrial control computer (ICC) technology in China has gone through several stages: the first generation of STD bus ICCs in the 1980s, and the second generation of IPC ICCs in the 1990s. The development of IPC ICCs, based on passive backplane systems, was driven by the desire to improve mean time between repairs (MTBL) and provide convenient system upgrades, as this architecture simplifies system updates and repairs while minimizing downtime. Another reason is that IPC ICCs have developed significantly alongside the PC industry, solving the problems of low cost and compatibility with PC hardware and software. Practice has proven that reliable and inexpensive ICCs are suitable for China's national conditions.
As early as 1994, the PICMG organization promptly introduced PCI technology into passive backplane structures, establishing the PICMG 1.0 standard based on ISA/PCI technology. Systems under the PICMG 1.0 standard architecture have the following main advantages:
1. Short system update and repair time;
2. It has excellent scalability;
3. It helps improve the overall system's heat dissipation performance;
However, after prolonged use, some defects were found in the physical architecture of the baseboard with expansion cards. For example, the gold fingers were prone to oxidation, and the slots were prone to loosening under vibration, making it unsuitable for corrosive and vibrating environments. Meanwhile, due to advancements in computer hardware platform technology, there was a need to enrich the functionality of existing buses. In response, the industry introduced CompactPCI technology based on the PICMG 2.0 specification. However, due to factors such as price and development difficulty, CompactPCI struggled to enter the mainstream market for some time. Therefore, Advantech launched the EVOC-EPI 1.0 bus to address this situation, thus extending the lifespan of IPC industrial control computers.
3. EVOC-EPI bus architecture industrial control computer
3.1 EVOC-EPI bus characteristics:
The EVOC-EPI 1.0 bus continues the PICMG 1.0 standard bus technology in terms of electrical signal characteristics. In terms of the plug-in connection method, it adopts two pairs of 120 and 90 pin or hole European card-type mechanical structure connectors. Each pair of connectors consists of three rows of pins or holes, which has high airtightness and corrosion resistance, further improving the reliability of industrial control computers, enhancing the system's resistance to vibration and shock, and minimizing system failures caused by vibration.
Functionally, starting from the system level that realizes the functions of the whole machine, the original bus signals are supplemented to make the system implementation more flexible and scalable.
(Figure 1)
3.2 Inherent defects of traditional PICMG/PIC/ISA bus gold finger connection method:
1. As hardware platform performance improves, power consumption also increases. The weight of the cooling system mounted on the CPU card inevitably increases, causing instability in the CPU card's center of gravity. This can easily lead to problems such as PCB deformation, broken wires, and poor contact, resulting in unstable operation.
2. In the traditional PICMG1.0 specification, the physical connection between the CPU card and the baseboard is a gold finger connection. The contact between the gold finger and the passive baseboard slot is the squeezing of the springs on both sides. During vibration and impact, momentary poor contact can cause the system to crash.
3. After the CPU card is connected to the motherboard slot, more than 50% of the gold finger surface is exposed to the air. Long-term use in humid or corrosive gas environments can easily lead to oxidation or corrosion, causing poor system contact.
4. The PCIMG 1.0 specification applies to platforms using AT power supplies. With the diversification of market demands, more and more manufacturers are requiring bus extensions to support dual power supply modes of AT/ATX.
5. The PICMG 1.0 specification supports PCI version 2.0, which cannot meet the power management requirements of PCI expansion cards with wake-up functionality for the system platform. Furthermore, PICMG 1.0 does not support the SMBUS bus, resulting in insufficient flexibility in the communication methods for the motherboard to manage various expansion cards.
6. As a complete system, the motherboard has multiple monitoring signals that need to be connected to cards installed on the front or rear panel of the chassis. Complete systems conforming to the traditional PICMG 1.0 specification use wired connections. This results in complex wiring within the chassis, reducing the overall heat dissipation performance and assemblability, thus significantly impacting the stability of the entire system.
(Figure 2)
3.3 Advantages of the EVOC-EPI bus
1. The EVOC-EPI bus uses European-style connectors for the CPU board and the baseboard. Each pair of connectors is interconnected through high-density and airtight pin connectors, with signal pins making 360° contact. This improves the system's resistance to vibration and shock, minimizing system failures caused by vibration. The signal pin contacts are sealed, effectively preventing the erosion of dust, corrosive gases, and humid air, thus improving the reliability of the system during long-term operation.
(Figure 3)
2. The EVOC-EPI bus supports the expansion of daughter card PME# power management functions and the addition of SMBus bus, making the communication management functions between various boards in the whole system more flexible and convenient.
3. The EVOC-EPI bus supports direct power supply to the CPU card via the bus interface by modifying the power pin definitions. It also adds control signals such as PS_ON for ATX power supplies, enabling the bus to support both AT and ATX power modes.
4. The EVOC-EPI bus adds system monitoring signals such as front panel buttons, indicator lights, and alarms, allowing for flexible expansion of these signals on the baseboard via the bus. The layout of the baseboard monitoring signal interfaces is modified according to the internal structure of different systems, ensuring low-density wiring inside the chassis and optimizing system heat dissipation.
5. The EVOC-EPI bus prioritizes high-speed signal routing in its signal distribution. This shortens the trace length of PCI signals from the bus expansion slot to the daughter card on the baseboard, reduces the impact of distributed capacitance on signal integrity, significantly improves PCI signal quality, and enhances system reliability. (Baseboard Figure 4)
(Figure 4 of the base plate)
4. Overall reliability of industrial control computers based on EVOC-EPI bus architecture
The EVOC-EPI bus architecture industrial PC, while inheriting the maintainability and expandability of the PICMG1.0 standard architecture, places particular emphasis on improving the overall system reliability, maintainability, and bus expandability. This can be seen in the following figure (Figure 5) of the EVOC-EPI 4U IPC industrial PC. Regarding vibration resistance, the CPU board and baseboard are connected using European connectors, and the CPU board also has two anti-vibration strips to prevent system instability caused by poor contact between the CPU board and baseboard during vibration. Two fans are installed on the front panel, one at the front of the motherboard and the other at the front of the hard drive bay. A temperature control module is installed on the front panel to display the CPU and system temperatures in real time and can also set an over-temperature alarm function. Furthermore, the low-density wiring within the chassis ensures smooth airflow, thus guaranteeing excellent heat dissipation and stability of the system. In terms of maintainability, since the CPU card's monitoring signal is connected to the interface header on the baseboard via the expansion bus, no headers for connecting to the monitoring board are needed on the board, making CPU card replacement more convenient and saving system maintenance time. In terms of bus functionality expansion, the EVOC-EPI bus fully supports PME# power management and SMBus bus, facilitating software-based management of the boards within the chassis. The EVOC-EPI bus optimizes traditional industrial control computers at the system level, making them more adaptable to the evolving needs of computer hardware platform technologies while maintaining the overall reliability and functional integrity required by current industrial control computers.
(Figure 5 of the complete machine)
5. End
With the continuous development of computer technology, people have increasingly higher requirements for the performance and stability of computer technology in industrial production processes. Currently, IPC industrial control computers based on the PICMG 1.0 standard architecture are becoming increasingly strained due to rising computer performance and applications in special environments. To address these issues, Advantech has continuously innovated and improved its products, creatively developing the EVOC-EPI 1.0 bus standard based on the PICMG 1.0 standard architecture. This extends the lifespan of IPC industrial control computers, enabling their widespread application in modern industrial automation and contributing to the national goal of "informatization driving automation."
References:
[1] PICMG1.0 Release Note Revision 2.0, October 10,1994
[2] CompactPCI Release Note for PICMG 2.0 Revision 2.1, September 2,1997
[3] Liu Xin, Industrialization and Application Prospects of New Generation Industrial Control Computers, China Computer Industry Association PICMG/PRC, October 21, 2004.
