FUNCTIONAL DESCRIPTION

The PCI-IDIO-16 is a low-cost, 6.8" card that provides isolated input and output for PCI-bus computers. The card has sixteen optically-isolated digital inputs for AC or DC control signals and sixteen isolated FET outputs. For safety reasons in working with AC voltages, insulating shields are provided with each card.

Inputs

The isolated inputs can be driven by either AC or DC signals and are not polarity sensitive. Input signals are rectified by a diode bridge and applied to a transistor circuit that provides constant current drive to the opto-isolator independent of the amplitude on the input. Input voltages of 2.5-50VDC or AC voltages of 2V- 36Vrms can be accepted. Inputs have a 0.2V hysteresis.

Each input circuit contains a software switchable slow/fast filter that has a 5 millisecond time constant. The filter must be selected for AC inputs in order to eliminate response to zero crossings. The filter is also valuable for use with slow DC input signals in a noisy environment. The filter may be switched out for DC inputs in order to obtain faster response. Filters are globally switched on or off in one group of 16 inputs.

Interrupts

Interrupts are enabled/disabled by software. When the change-of-state detection circuit is enabled, the card asserts an interrupt whenever any of the sixteen inputs change state. Once an interrupt has been generated and serviced, it must be cleared by system software. This feature greatly frees up system resources by eliminating the need for constant polling to see when an input has changed state.

Outputs

The FET outputs are comprised of two groups of four completely isolated outputs and four outputs that share a common return. The outputs are all off at power-on. Data to the outputs is latched. Capable of 1A carry current at up to 50VDC. FETs are fully protected against short circuit, over-temperature, ESD damage, and have active clamping above 50VDC.

Connections

The I/O is accessed via a 78 pin DBF connector on the mounting bracket of the card. A molded breakout cable (model CAB78-37/2) is optionally available that divides the 78 pins into two DB37F connectors. Also available is a kit (model STB-37/2 Kit) which includes the cable and two STB-37 Screw Terminal Cards that mount into an included one-foot length of Snap-Trak.

Digital Inputs

Protected FET Outputs

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