{"product_id":"allen-bradley-1756-cnb-d-controllogix-controlnet-communication-module","title":"Allen-Bradley 1756-CNB\/D ControlLogix ControlNet Communication Module","description":"\u003ch1 class=\"PDq2pG_selectionAnchorContainer\"\u003eAllen-Bradley 1756-CNB\/D ControlLogix ControlNet Communication Module\u003cspan class=\"PDq2pG_selectionAnchor\"\u003e\u003c\/span\u003e\n\u003c\/h1\u003e\n\u003cp\u003eThe\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003eAllen-Bradley 1756-CNB\/D\u003c\/strong\u003e, also cataloged as the\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003e1756-CNB\/D\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eControlNet communication module, operates as a dedicated hardware interface for deterministic ControlNet frame exchange between ControlLogix backplane controllers and a single-channel ControlNet network within a ControlLogix chassis system. Configured for scheduled and unscheduled communication processing, the\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003e1756-CNB\/D\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eprovides direct physical and protocol-level execution of ControlNet data transfer at the network interface layer.\u003c\/p\u003e\n\u003cp\u003eWithin the\u003cspan\u003e \u003c\/span\u003e\u003cspan class=\"hover:entity-accent entity-underline inline cursor-pointer align-baseline\"\u003eRockwell Automation\u003c\/span\u003e\u003cspan\u003e \u003c\/span\u003eControlLogix platform, the module maps controller task execution to ControlNet media scheduling, enabling synchronized data propagation between controller nodes and distributed devices over a single deterministic channel.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003eHardware Specifications\u003c\/h3\u003e\n\u003ctable class=\"w-fit min-w-(--thread-content-width)\"\u003e\n\u003cthead\u003e\n\u003ctr class=\"firstRow\"\u003e\n\u003cth class=\"last:pe-10\"\u003eParameter\u003c\/th\u003e\n\u003cth class=\"last:pe-10\"\u003eSpecification\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eModel\u003c\/td\u003e\n\u003ctd\u003e1756-CNB\/D\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eAllen-Bradley\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOrigin\u003c\/td\u003e\n\u003ctd\u003eUSA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNetwork Type\u003c\/td\u003e\n\u003ctd\u003eControlNet single channel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eConnections\u003c\/td\u003e\n\u003ctd\u003eUp to 99\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eIsolation\u003c\/td\u003e\n\u003ctd\u003e30 V continuous basic insulation (ControlNet to backplane, USB to backplane)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eElectromagnetic Immunity\u003c\/td\u003e\n\u003ctd\u003e10 V\/m (80–2000 MHz), 3 V\/m (2000–2700 MHz)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompliance\u003c\/td\u003e\n\u003ctd\u003eIndustrial EMC standards\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRepairability\u003c\/td\u003e\n\u003ctd\u003eReplaceable module\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003chr\u003e\n\u003ch3\u003eControlLogix Backplane Deterministic Communication Behavior\u003c\/h3\u003e\n\u003cp\u003eThe 1756-CNB\/D executes ControlNet communication through deterministic scheduling aligned with ControlLogix controller scan cycles. Data transfer timing is governed by backplane arbitration logic, ensuring consistent frame execution for both scheduled and unscheduled messaging.\u003c\/p\u003e\n\u003cp\u003eThe module supports single-channel ControlNet topology without redundant media paths. Network synchronization is maintained through cyclic scheduling, where controller output data and input sampling are aligned to fixed network time slots.\u003c\/p\u003e\n\u003cp\u003eUSB service interface operates independently of cyclic ControlNet traffic and is used for configuration and diagnostic-level access without disrupting scheduled communication flows.\u003c\/p\u003e\n\u003chr\u003e\n\u003ch3\u003eFrequently Asked Questions (FAQ)\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Does the 1756-CNB\/D support hot-swapping in a live ControlLogix system?\u003c\/strong\u003e\u003cbr\u003eA: Yes. The module supports hot insertion and removal. Reinitialization is handled through chassis backplane rescan and controller reconfiguration synchronization.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What limits the number of supported ControlNet connections?\u003c\/strong\u003e\u003cbr\u003eA: The module supports up to 99 connections, limited by ControlNet scheduling bandwidth and backplane communication resources.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Does the CNB\/D provide redundancy across ControlNet channels?\u003c\/strong\u003e\u003cbr\u003eA: No. The CNB\/D operates on a single-channel ControlNet architecture without redundant media paths.\u003c\/p\u003e\n\u003chr\u003e\u003chr\u003e\n\u003ch3\u003eField Installation Guidelines\u003c\/h3\u003e\n\u003cp\u003eInstall the module into a compatible ControlLogix chassis slot ensuring full engagement of the backplane connector to maintain deterministic timing alignment. ControlNet coaxial cabling must maintain impedance consistency and continuous shielding integrity across trunk and drop segments.\u003c\/p\u003e\n\u003cp\u003eRoute ControlNet media away from high-current conductors to reduce electromagnetic coupling effects. Shield grounding must be implemented using a single-point earth reference to prevent ground loop formation in the communication network.\u003c\/p\u003e\n\u003cp\u003eVerify firmware compatibility between controller, chassis, and communication module prior to commissioning to ensure proper backplane synchronization and network scheduling consistency.\u003c\/p\u003e","brand":"Allen-Bradley","offers":[{"title":"Default Title","offer_id":43577372344410,"sku":"1756-CNB\/D","price":123.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0612\/4601\/3530\/files\/1756-CNBR.jpg?v=1777530544","url":"https:\/\/www.plcmasters.com\/products\/allen-bradley-1756-cnb-d-controllogix-controlnet-communication-module","provider":"PLC Masters Ltd.","version":"1.0","type":"link"}