PC/104

PC/104 is a standard and form factor for PC cards and embedded systems published in 1992. It is a miniaturized version of a PC that meets industrial requirements for robustness, reliability and longevity. The name is derived from the 104 pins of an interboard connector (ISA) in the original specification, although the standard has evolved over time to include other connectors and bus types as well. 

PC/104 modules are designed to be stacked on top of one another, allowing for easy expansion and customization of embedded systems. The stacking feature enables developers to mix and match different modules to meet specific application requirements, such as adding processing power, I/O interfaces, or communication capabilities. 

Form Factor and Physical Characteristics: PC/104 is a compact, rugged, and modular embedded computer standard. The original PC/104 form factor measures 3.550 × 3.775 inches (90 × 96 mm), which is smaller than a typical desktop PC motherboard. 

Stackable Architecture

PC/104 modules are designed to be stacked on top of one another like building blocks, forming a stack of interconnected modules. This stacking feature facilitates modular expansion and customization of embedded systems. This allows the boards to be fastened to each other using standoffs. This stackable bus connector system provides a rugged and stable mounting solution. 

Bus Architecture

PC/104 originally utilized the ISA (Industry Standard Architecture) bus architecture. However, newer versions have incorporated more modern bus standards such as PCI (Peripheral Component Interconnect) and PCI Express. The bus architecture allows for communication between the CPU and peripheral devices/modules stacked on the PC/104 stack. The PC/104 standard originally defined a stackable ISA bus, which was a popular choice for embedded applications due to its simplicity and reliability. As technology advanced and the need for higher bus throughput performance arose, the PC/104 Consortium developed the PC/104-Plus and PCI-104 specifications.  

Ruggedness and Embedded Applications

PC/104's rugged design makes it suitable for specialized environments where a small, durable computer system is required. Its use in industrial markets is widespread due to its reliability and long life. The stackable design eliminates the cost and bulk of backplanes and card cages, which is particularly beneficial for applications with limited space. They are built using components and may feature conformal coating to protect against moisture, dust, and temperature extremes. 

Peripheral Interfaces

PC/104 modules offer a wide range of peripheral interfaces to connect to external devices and sensors. These interfaces can include Serial ports (RS-232, RS-485, RS-422), USB (Universal Serial Bus), Analog I/O (Analog-to-Digital Converters, Digital-to-Analog Converters) or other specialized interfaces for specific applications (e.g., fieldbus interfaces, video interfaces). 

Industrial Automation and Control Systems

PC/104 is extensively used in industrial automation and control systems where reliability, and compactness are essential. Its ability to withstand harsh environments, resistance to shock and vibration, and modular design make it ideal for applications in manufacturing plants, process control, robotics, and monitoring systems. It serves as the backbone of PLCs (Programmable Logic Controllers), SCADA (Supervisory Control and Data Acquisition) systems, and distributed control systems (DCS), enabling real-time data acquisition, analysis, and control. 

Industrial Communication

PC cards in PC/104 format were used for a long time to integrate systems into industrial fieldbus and Real-Time Ethernet networks. Over time, however, more compact PCI- or PCIe-based form factors have become established. 

Robotics

PC/104 serves as the computing platform for robotics and automation applications, including robotic arms, autonomous vehicles or industrial robots. It provides the processing power and connectivity required for sensor integration, motion control, path planning, and decision-making algorithms. 

Therefore, PC/104 has various applications in a wide range of industries and sectors, providing reliable computing solutions for diverse applications such as industrial automation, transportation, energy, robotics, and IoT. Its form factor and compatibility make it a preferred choice for PC-based automation in challenging environments. 

PC/104 is highly valued in specialized and industrial applications for its rugged and modular design. Its modularity allows for the stacking of various boards, such as CPU, power supply, and peripheral boards, creating a customized embedded system without needing a backplane, enhancing system robustness. PC/104's standardized form factor and connectors further enable rapid prototyping and development, reducing time-to-market. It supports a long product lifecycle, often exceeding 10 years, ensuring long-term availability of parts and upgrades. The extensive ecosystem of compatible boards and support for various bus structures like ISA, PCI, and PCIe provides designers with numerous off-the-shelf options, facilitating development and system upgrades.