Description
Introduction to the PCIe-IDIO-24 Isolated Digital Input/Output Card
This PCIe-IDIO-24 is a x1 lane PCIe isolated digital input and FET output board with Change of State Detection and isolated FET high-side switches. The board has twenty four optically-isolated input circuits for AC or DC control signals and twenty four isolated FET high-side switches. The board occupies sixteen consecutive addresses in I/O space. Read and write operations may be 8, 16, or 32 bits wide. Several versions of this board are available. The PCIe-IDIO-24 also has eight TTL level non-isolated I/O lines. Model PCIe-IDIO-12 provides twelve isolated inputs and outputs and four TTL/CMOS I/O lines.
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 the inputs of opto-isolators. A 1.8k 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 3V to 31VDC (or 40-10kHz RMS). To extend the input voltage range, you may connect external resistors in series. Inputs can be configured to generate an IRQ when the input changes from active-to-inactive, inactive-to-active, or both in groups of eight bits.
Each input bank (12×2) contains a switchable filter that has a 4.7 millisecond time constant. Without filtering, rise time response is 10us fall time is 30us. The filter must be selected for AC inputs in order to eliminate the on/off response to the AC zero crossing. The filter is also valuable for use with slow DC input signals in a noisy environment. The filters may be switched out for DC inputs in order to obtain faster response. Filters are selected by the user’s software.
Interrupts
When configured by the user’s software, the board asserts an interrupt whenever any enabled inputs change state from HIGH (more than 3V) to LOW (less than 3V), LOW to HIGH, or both. This is called Change-of-State (COS) detection. See the programming section for a discussion of the COS interrupt management scheme. 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.
Digital ∫ Features
Models include new Digital Integration Features on 8 bits of input and 8 bits of output.
- Inputs: Enhanced Change-of-State IRQs can be enabled on a bit-by-bit basis, with a selectable (rising/falling) edge. Separately enabled per-bit edges are counted with an optional overflow IRQ. Low-side and high-side pulse widths are measured with a resolution as fine as 8ns. These measurements automatically provide both frequency and duty cycle measurements for waveforms up to 65.5 MHz.
- Outputs: Individual rising-or-falling pulses can be generated, individually or simultaneously on up to 8 output bits, with durations controllable with 8ns resolution. Sequential pulses or continuous frequencies (with programmable duty-cycle) can also be output.
- EZUpdate: FPGA supports EZUpdate allowing new FPGA code to be written via software across the PCI Express bus, allowing field upgrade with new features.
For details regarding Digital Integration Feautres please refer to the Digital Integration Features Reference.
Outputs
The PCIe-IDIO-24 features fully protected and isolated high side power MOSFET switch outputs which are de-energized at power-up to prevent an unintended control output signal. They are capable of switching customer supplied voltages of 5 to 34VDC, at up to 2A. The FET outputs are comprised of three groups of four completely isolated outputs and four outputs that share a common return. The outputs are all off at power-on. FETs are fully protected against short circuit, over-temperature, ESD damage, and have active clamping above 40VDC.
The Card and Connectivity
The card is 6.6 inches in length and 4.2 inches seated height. 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) that divides the 78 pins into two DB37F connectors is optionally available. 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.