7 ELECTRONICS AND INTERFACING

This brief introduction to the electronics most often needed by digital I/O board users covers a few key concepts.

IMPORTANT NOTE

WHENEVER AN 82C55 IS POWERED-ON OR RESET, ALL PINS ARE SET TO HIGH-IMPEDANCE INPUT. FOLLOWING STANDARD TTL FUNCTIONALITY, THESE INPUTS WILL TYPICALLY FLOAT HIGH, AND MAY HAVE ENOUGH DRIVE CURRENT TO TURN ON EXTERNAL DEVICES.

The implications of this is that if you have output devices such as solid state relays, they may be switched on whenever the computer is powered on or reset. To prevent unwanted switching and to drive all outputs to a known state after power on or reset, pull all pins either high or low through a 2.2 K resistor.

7.1 PULL UP & PULL DOWN RESISTORS

Whenever the board is powered on or reset, the control register is set to a known state. That state is all ports go to the input state.

The nature of the input means it will typically float high. However, depending on the drive requirements of the device you are driving, they may float up or down. Which way they float is dependent on the characteristics of the circuit and the electrical environment; and may be unpredictable. This is why it often appears that the board outputs have gone 'high' after power up. The result is that the controlled device gets turned on. That is why you need pull up/down resistors.

Shown in Figure 7-1 is an 82C55 digital output with a pull-up resistor attached.

The pull-up resistor provides a reference to +5V. The value of 2.2K ohms requires only 2.3 mA of drive current.

If the board is reset and enters high impedance input, the line is pulled high. At that point, both the board AND the device being controlled will sense a high signal

Figure 7-1. Pull-up Resistor

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Omega Engineering PCI-DIO96 user manual Electronics and Interfacing, Pull UP & Pull Down Resistors
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PCI-DIO96 specifications

The Omega Engineering PCI-DIO96 is a versatile and high-performance digital input/output board designed for a wide range of industrial automation and data acquisition applications. With its robust features and advanced technologies, the PCI-DIO96 stands out in the field of digital I/O expansion cards.

At the core of the PCI-DIO96 is its capability to handle 96 digital I/O channels, making it suitable for applications that require extensive control and monitoring. The board is equipped with 96 lines that can be individually configured as input or output, providing flexibility to manage various digital devices such as sensors, valves, and relays. This configuration is particularly beneficial in complex systems where a mix of digital signals is needed.

One of the most notable characteristics of the PCI-DIO96 is its high-speed operation. The board supports data transfer rates that can accommodate demanding applications, enabling rapid response times crucial in industrial environments. This high-speed capability ensures that it can keep up with the fast-paced demands of modern automation processes.

The PCI-DIO96 also includes additional features such as programmable timers and counters, allowing for precise control and measurement of time-sensitive processes. This performance enhancement is especially useful in applications requiring synchronization of multiple digital signals or sequential operations.

Another significant advantage of the PCI-DIO96 is its compatibility with various operating systems and widely-used programming environments. It can be seamlessly integrated with popular data acquisition and control software, providing users with a familiar setup process. This ease of integration diminishes the time required for installation and setup, allowing for quicker deployment in projects.

The hardware design of the PCI-DIO96 also emphasizes reliability and ease of use. The board is built with durable components to withstand the rigors of industrial settings, ensuring longevity and reliability in various conditions. Additionally, its straightforward installation process translates into minimal downtime during setup.

In conclusion, the Omega Engineering PCI-DIO96 is a powerful digital I/O board that combines extensive channel capacity, high-speed performance, and robust features. Its versatility makes it an ideal choice for diverse applications in industrial automation, offering reliability and ease of integration that professionals in the field seek for their projects. Whether for monitoring, control, or data acquisition, the PCI-DIO96 remains a trusted solution for engineers and technicians alike.
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