Allen-Bradley 1756-IG16 ControlLogix Digital Input Module

The Allen-Bradley 1756-IG16, also cataloged as the 1756-IG16 Digital Input Module, operates as a dedicated hardware component for high-speed TTL signal interface within ControlLogix backplane platforms. The module processes 5 VDC low-voltage logic signals across 16 sourcing input points, converting transistor-transistor logic (TTL) levels into internal backplane status data. The unit establishes direct interface execution for electronic sensors, optical encoders, and TTL-compatible field devices requiring rapid state transitions without signal distortion.

Hardware Specifications

ControlLogix System Architecture & Backplane Protocol Features

The module communicates over the local ControlLogix backplane bus utilizing high-velocity CIP (Common Industrial Protocol) framing. Backplane bus communication velocity guarantees low deterministic latency during discrete state updates. Scalable I/O density features allow seamless integration of high-density 5 VDC TTL input channels while maintaining synchronous cyclic data transmission to the controller at configured Requested Packet Interval (RPI) rates. Firmware flash compatibility enables online module diagnostics and platform synchronization through Studio 5000 Logix Designer without interrupting rack power.

Frequently Asked Questions

Q: Can the 1756-IG16 module be removed or inserted under power (RIUP)?

A: Yes, the module supports Removal and Insertion Under Power (RIUP) within a powered ControlLogix chassis. However, 5 VDC field signal wiring connected to the Removable Terminal Block (RTB) should be safely isolated to prevent unwanted input state glitches or pin electrical stress during insertion.

Q: What type of field signal levels is the 1756-IG16 designed to accept?

A: The module is engineered specifically for 5 VDC TTL (Transistor-Transistor Logic) sourcing signals. Connecting 24 VDC field signals directly to this module will damage internal low-voltage input circuitry.

Field Installation Guidelines

• Verify backplane chassis grounding strictly complies with IEEE 1100 standards; maintain a dedicated low-impedance copper ground connection between the chassis frame and the main panel star ground point.
• Ensure the 20-pin Removable Terminal Block (RTB) retention latches snap securely into the top and bottom chassis keyways before powering field circuits.
• Route 5 VDC TTL signal cables in separate wiring trunks isolated from 120/240 VAC power distribution lines and VFD motor cables to prevent capacitive noise coupling.
• Connect shielded signal wiring at a single enclosure ground terminal to minimize common-mode noise on low-voltage logic inputs.