The Measurement Computing PCI-DIO24 is a 24-channel digital I/O board for PCI bus computers delivering independent input/output configuration across three 8-bit ports using the industry-standard 82C55 programmable peripheral interface chip. Each of the 24 digital I/O lines configures independently as input or output via software, with Port C subdividing into two 4-bit ports. CMOS TTL level logic operates across bi-directional pins accessible through a rear-panel 37-pin male D-type connector. The board supports PCI Specification 2.1 and operates in both 3.3 V and 5 V PCI slots, with all I/O lines defaulting to high impedance input mode on power-up or reset.
Technical Specifications
Digital I/O Configuration
• 24 independent I/O lines organized as three 8-bit ports (A, B, C)
• Port C subdivides into Port C-HI and Port C-LO (4-bit each)
• Each port independently configured for input or output
• 82C55 Mode 0 programming supported
• CMOS TTL logic level
• Default state: high impedance input on all bits
• Bi-directional pin operation
Electrical Performance
• Power consumption: 240 mA typical, 350 mA maximum at +5 V
• Output drive (PCI-DIO24H): 64 mA sink current, 15 mA source current
• Input thresholds: 2.2 V minimum high, 0.8 V minimum low
• Output levels (PCI-DIO24H): 3.7 V minimum high @ −2.5 mA, 0.4 V maximum low @ 2.5 mA
• Optional 2.2 kΩ pull-up/pull-down resistor networks available per port
Interface & Physical
• PCI bus host interface, x1 lane PCIe variant available
• 37-pin male D-type connector, rear-accessible
• Dimensions: 167.4 × 111.2 × 18.72 mm
• Operating temperature: 0 °C to 50 °C
– Key Features
• Dual voltage PCI slot compatibility (3.3 V and 5 V)
• Flexible software-configurable port arrangement
• Industry-standard 82C55 chip ensures vendor interoperability
• Open resistor locations for pull-up/pull-down customization
– Typical Applications
Industrial control, laboratory automation, sensor interfacing, relay switching, and discrete signal acquisition in test systems requiring independent channel configuration.
– Compatibility & Integration
Pin and software compatible with Measurement Computing’s CIO-DIO24 ISA series and other 82C55-based boards. Windows 2000 and NT drivers available with sample code. Software written for USB-DIO24/37 and PCI-DIO24 devices transfers directly to PCIe-DIO24 variants.
