The Keithley / MetraByte PIO-24 is a parallel digital interface board that delivers 24 lines of TTL/CMOS-compatible digital I/O for IBM PC and compatible systems. It emulates the Intel 8255 Programmable Peripheral Interface in MODE 0, providing flexible configuration across three ports (PA, PB, and PC, with PC subdividing into two 4-bit half ports) via a 10-bit I/O address decode. The board connects through a standard 37-pin D-type male connector and supports both DriverLINX and ActiveX Direct I/O software interfaces for rapid hardware access and OS-independent operation.
## Technical Specifications
• **I/O Architecture:** 24 digital lines across three TTL/CMOS ports with independent programmability
• **Interface:** 8-bit ISA peripheral bus to PC
• **Address Decode:** 10-bit I/O address decode
• **Interrupt Support:** Dedicated interrupt input channel with enable control
• **Power Supply:** +5V, +12V, −12V from host PC
• **Operating Temperature:** 0°C to 50°C
• **Storage Temperature:** 0°C to 70°C
• **Humidity:** 0 to 95% non-condensing
## Key Features
• Maximum output current 25 mA per line
• Input high voltage (VIH) minimum 2.0V; input low voltage (VIL) maximum 0.8V
• Current sink capability: 6 mA minimum @ 0.33V, 20 mA maximum @ 1.0V
• Input current (IIH) ±1 µA @ 2.7V
• Intel 8255 MODE 0 emulation for legacy software compatibility
• Rear-panel connector for cable-based external device connections
• Port C subdivisions enable flexible half-port configuration
## Typical Applications
Data acquisition, digital device control, experimental automation, and legacy system integration within PC-based platforms.
## Compatibility & Integration
Designed for IBM PC, PC-XT, PC-AT, and compatibles. Ships with DriverLINX software for Windows 95/98 and Windows NT. ActiveX Direct I/O provides alternative access without interrupt support. Mating connector is standard 37-pin D female (e.g., SFC-37). Optional cables include C-1800 (unshielded, 18-inch ribbon) and S-1800 (shielded variant).
