Description
Note: Many products are not yet listed. Please contact us for more product information. Our supply channels are constantly expanding, and we currently have 20 stable shared supply channels. Please confirm the model, product, price, and all other necessary information with customer service before placing an order. We offer new, refurbished, and used products, and prices are adjusted according to the year of the item you require.
Key Technical Specifications
| Parameter | Value |
|---|---|
| Network | ControlNet, 5 Mbps fixed baud rate |
| Media Interface | Single BNC (non‑redundant) |
| NAP Port | Shielded RJ45 NAP (Network Access Port) for programming |
| Supported Connections | 40–48 recommended Logix connections, max 64 total |
| Max Nodes on Network | 99 nodes |
| Cable Type | 1786‑RG6 quad‑shield RG6 coax |
| Backplane Draw | 970 mA @ 5.1 V DC; 1.7 mA @ 24 V DC |
| Power Dissipation | 5.1 W |
| Mounting | Any slot in 1756 ControlLogix chassis |
| Operating Temperature | 0 °C to +60 °C, non‑condensing |
| Storage Temperature | −40 °C to +85 °C |
| Humidity | 5–95% RH, non‑condensing |
| Certification | Class I Div 2, CE |
| Weight | 0.26 kg |
Product Introduction
The Allen‑Bradley 1756‑CNB/D is a Series D non‑redundant ControlNet bridge module for ControlLogix racks. It connects the Logix controller to ControlNet remote I/O, drives, and peer PLCs for scheduled deterministic I/O exchange and unscheduled messaging. The built‑in NAP port lets technicians connect RSLogix 5000 directly to the ControlNet network without disturbing the main coax trunk. Series D firmware adds improved diagnostic counters and network scheduling stability compared to older C revisions. It is not redundant media; redundant ControlNet requires 1756‑CNBR.
1756-CNB/D
1756-CNB/D
1756-CNB/D
1756-CNB/D
1756-CNB
Application Scenarios & Field Experience
Many legacy ControlNet systems mix C and D revisions. Mismatched firmware can cause schedule skew and intermittent I/O drops even if the module appears online. The D revision is widely used as a drop‑in spare for existing ControlLogix ControlNet racks.
- Automotive assembly lines: Scheduled I/O for robot I/O blocks and variable‑frequency drives.
- Oil & gas skids: Remote ControlNet I/O for valve packages and local ESD interfaces.
- Food & beverage batch systems: Deterministic control of fillers, conveyors and packaging machines.
- Power plant auxiliary systems: ControlNet remote I/O racks for BOP instrumentation.
In my experience, a bottling line had a 1756‑CNB/D lock up after a coax surge caused network noise. The maintenance team swapped the spare D‑series module, set the matching ControlNet node address, downloaded the module schedule, and verified all scheduled I/O tags resumed without fault. The line recovered quickly, and they added coax surge protection to the trunk tap.
Standard Operating Procedure (SOP) for Quality Control
- Visual & Origin Inspection: Check OEM label, serial number, BNC connector, NAP RJ45, status LEDs and backplane edge fingers. Reject units with cracked BNC or bent pins.
- Live Rig Testing: Install in 1756 chassis, power up, configure node address, connect to ControlNet network, validate scheduled I/O and NAP programming access.
- Firmware / Revision Verification: Record FRN firmware revision, confirm compatibility with RSLogix 5000 and the existing ControlNet schedule.
- ESD‑Safe Packaging: Protect edge connector and BNC port, place in static shielding bag, foam packed rigid carton with ESD warning.
Frequently Asked Questions (FAQ)
Q1: What is the difference between 1756‑CNB/D and 1756‑CNBR/D? A: 1756‑CNB/D = single BNC, non‑redundant media. 1756‑CNBR/D = dual BNC A/B redundant ControlNet media. They are not interchangeable for redundant network layouts. Q2: What warranty applies to this Allen Bradley 1756‑CNB/D? A: We offer a 12‑month warranty. Warranty covers hardware defects under rated operating conditions. Damage from coax overvoltage, misconfigured node address, or firmware mismatch is excluded. Q3: Is this 1756‑CNB/D stocked? A: This is discontinued legacy spare. Stock is limited. Confirm lead time before scheduling downtime. Drop‑in replacement part is 1756‑CN2. Q4: Do I need to re‑download the full project after replacing this module? A: You only need to match the node address and firmware revision. The ControlNet schedule is stored in the controller. Verify scheduled I/O after swap. Q5: Can I hot‑swap this module while the ControlLogix rack is powered? A: Hot swap is supported on 1756 chassis. However, all ControlNet scheduled I/O controlled by this module will fault during replacement. Lock down interlocks before removal.
