The Allen-Bradley 1756-IB16IF, also cataloged as the 1756-IB16IF Fast Digital Input Module, accepts 10-30 VDC field signals through 16 individually isolated inputs and transfers input states to the ControlLogix backplane. Rockwell Automation identifies it as a fast peer control input module.

Model Reference

The 1756-IB16IF is a ControlLogix 16 point digital input module with individually isolated inputs. Rockwell Automation specifies a 12/24 VDC sink/source input category, a 10-30 VDC operating range, and high-speed input processing with configurable filtering.

The product uses a 36-pin connection arrangement and is compatible with the 1756-TBCH and 1756-TBS6H removable terminal blocks. Rockwell Automation currently lists the 1756-IB16IF as an active product.

Hardware Specifications

The electrical ratings, isolation values, timing, backplane load, filtering range, and terminal block compatibility are specified in Rockwell Automation technical data.

High-Speed I/O and Peer Control

The 1756-IB16IF is designed for fast digital input acquisition. Its hardware input delay is specified at 14 us nominal and 23 us maximum for both off-to-on and on-to-off transitions before the selected filter interval is added.

The input filter is software configurable from 0 to 30,000 us. A shorter filter setting reduces input filtering delay, while a longer setting increases signal qualification time. The correct setting depends on the field signal characteristics and required event response.

The module supports peer control operation within the ControlLogix architecture. It also provides software-configurable change-of-state operation and input timestamping. Timestamp accuracy is specified at +/-4 us for input frequencies below 4 kHz and +/-13 us above 4 kHz.

Backplane Communication and Electrical Isolation

The module transfers input states through the ControlLogix backplane and draws 275 mA from the 5.1 VDC supply and 3 mA from the 24 VDC supply. Total backplane power is specified at 1.47 W.

All 16 inputs are individually isolated. Rockwell Automation specifies 250 V continuous reinforced insulation between inputs and the backplane, and 250 V continuous basic insulation between individual input channels.

The input architecture is 12/24 VDC sink/source. This allows the field circuit polarity arrangement to be selected according to the connected device and wiring design, within the published input specifications.

Firmware and ControlLogix Integration

The 1756-IB16IF is integrated into the ControlLogix I/O architecture through the controller backplane. Rockwell Automation provides Add-On Profiles and EDS files specifically for this catalog number.

When changing controller firmware, Logix software versions, or module configuration, the installed I/O profile should be checked before commissioning. The module's fast timing functions and peer control configuration are software dependent.

Ordering Information

• 1 x Allen-Bradley 1756-IB16IF ControlLogix 16 Point Fast Digital Input Module
• 1 x 1756-IB16IF module assembly
• 1 x Compatible removable terminal block, 1756-TBCH or 1756-TBS6H, selected separately when required
• 1 x ControlLogix chassis position is required
• Field wiring, interface modules, and external power components are separate system items unless specifically configured

Installation and Wiring Guidelines

Input wiring

• Verify the field signal polarity and voltage before connecting the module.
• Keep the applied input voltage within 10-30 VDC.
• Use conductors sized for the connected field devices and installation conditions.
• Route input wiring separately from high-energy switching conductors where practical.

High-speed signals

• Use the shortest practical field wiring path for high-speed signals.
• Avoid unnecessary cable loops and parallel routing near high-current conductors.
• Select the software input filter according to the required pulse width and signal noise characteristics.
• Do not use excessive filtering where short-duration events must be detected.

Channel isolation

• Treat each input as an individually isolated channel.
• Verify the voltage relationship between separate field circuits before wiring them to different inputs.
• Maintain the specified isolation arrangement when interfacing circuits with different electrical references.

Grounding and shielding

• Apply cable shielding and grounding according to the ControlLogix installation design.
• Avoid unintended shield-current paths through multiple grounding points.
• Confirm chassis and power-supply grounding before applying field power.

Frequently Asked Questions

• How many input channels does the 1756-IB16IF provide?
  The module provides 16 individually isolated digital input channels. Its input category is 12/24 VDC sink/source with a 10-30 VDC operating range.
• What makes the 1756-IB16IF a fast input module?
  The specified hardware delay is 14 us nominal and 23 us maximum for both input transitions, before the configured filter interval is applied.
• What is the input voltage range?
  The module accepts 10-30 VDC signals with a nominal input voltage of 24 VDC.
• Are the 16 input channels isolated from each other?
  Yes. Rockwell Automation specifies 250 V continuous basic insulation between individual input channels.
• What is the backplane current draw?
  The module draws 275 mA at 5.1 VDC and 3 mA at 24 VDC. Total backplane power is specified as 1.47 W.
• Can the input filter be adjusted?
  Yes. The input filter is user configurable from 0 to 30,000 us, allowing the signal qualification period to be matched to the application.
• Does the module support input timestamping?
  Yes. Timestamp accuracy is specified at +/-4 us for inputs below 4 kHz and +/-13 us for inputs above 4 kHz.
• Which terminal blocks are compatible?
  Rockwell Automation lists 1756-TBCH and 1756-TBS6H removable terminal blocks for the 1756-IB16IF. The module occupies one chassis slot.