PCI-IIRO-8 Acces Isolated Digital Input/Output Card

The Access PCI-IIRO-8 / PCI-IIRO-16 Isolated Digital Input/Output Cards are half-size cards that provide isolated input and output for PCI-Bus computers. The cards have eight or sixteen optically-isolated digital inputs for AC or DC control signals and eight or sixteen electro-mechanical relay outputs. PCI-IIRO-8 occupies four consecutive eight-bit registers in I/O space. PCI-IIRO-16 occupies eight consecutive eight-bit registers in I/O space.

Inputs

The isolated inputs can be driven by either AC or DC and are not polarity sensitive. Input signals are rectified by a diode bridge and applied to the inputs of opto-isolators. A 470 ohm resistor in series provides current limiting. Standard 12/24 AC control transmitter outputs can be accepted as well as DC voltages. The input voltage range is 5V to 24V (rms). To extend the input voltage range, you may connect external resistors in series.

Each input circuit contains a switchable slow/fast filter that has a 10 millisecond (PCI-IIRO-8) or 5 millisecond (PCI-IIRO-16) time constant. (Without filtering, the response is 20 microseconds.) 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. For the PCI-IIRO-16 the filters are globally controlled by software. For the PCI-IIRO-8 the filters can also be individually selected by switches on the card.

Interrupts

Interrupts are enabled/disabled by software. When the change-of-state detection circuit is enabled, the card asserts an interrupt whenever one or more of the interrupts changes 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 electro-mechanical relay outputs of the PCI-IIRO-8 are comprised of five form C SPDT outputs and three Form A SPST (normally-open) type. The outputs of the PCI-IIRO-16 are divided into two groups of eight, each group being similar to the PCI-IIRO-8. The relays are all de-energized at power-on. Data to the relays is latched.

Connections

For the PCI-IIRO-8, I/O is accessed via a 37 pin DBF connector on the mounting bracket of the card. For the PCI-IIRO-16, 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.