Allen-Bradley 1783-US16T Industrial Ethernet Switch – Stratix 2000

Allen-Bradley 1783-US16T — 16-Port Unmanaged Switch in EtherNet/IP Control Architectures

The Allen-Bradley 1783-US16T is a 16-port, 10/100BASE-TX unmanaged industrial Ethernet switch belonging to the Rockwell Automation Stratix 2000 series. Within a control loop, this device operates at OSI Layer 2 as a wire-speed frame forwarder, providing deterministic, store-and-forward switching for EtherNet/IP implicit (I/O) and explicit (information) messaging between PLCs, drives, I/O adapters, and HMI nodes. Unlike managed switches that introduce configurable latency through VLAN processing or QoS queuing, the 1783-US16T delivers a fixed, predictable forwarding path — a property that is architecturally significant in time-critical motion and safety applications where jitter budgets are measured in microseconds.

In a typical ControlLogix or CompactLogix topology, the 1783-US16T serves as the device-level aggregation point: all field devices connect to its 16 RJ45 ports, and the uplink feeds into a managed distribution switch or directly into the controller’s embedded EtherNet/IP port. Because the switch performs hardware-based MAC address lookup at 2.38 Mpps forwarding rate against a 2,000-entry CAM table, unicast EtherNet/IP I/O frames are switched without flooding, preserving available bandwidth for other nodes on the segment. This is particularly relevant in high-density I/O panels where 12–16 Point I/O adapters share a single network segment.

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Technical Parameters

Hardware Logical Analysis

The 1783-US16T is built around a single-chip, application-specific integrated circuit (ASIC) switch fabric that implements a shared-memory architecture. All 16 ports feed into a common 1 Mbit packet buffer managed by a central arbiter. The arbiter resolves port contention using a round-robin scheduling algorithm, which distributes buffer access fairly across all active ports and prevents any single high-traffic port from monopolizing egress bandwidth — a failure mode common in cheaper commodity switches that use output-queued architectures without backpressure.

EMC Design: The PCB layout follows a split-plane strategy: the analog PHY circuitry and the digital switching ASIC occupy separate ground planes connected at a single star point near the power entry. Each RJ45 port incorporates integrated magnetics (Bob Smith termination topology) with 1,500 V isolation between the cable-side and logic-side circuits. This arrangement attenuates common-mode noise injected from cable runs — a practical concern in environments where Ethernet cables run parallel to 400 V motor power cables in shared cable trays. The chassis is bonded to functional earth (FE) through a dedicated terminal, providing a low-impedance path for high-frequency interference currents that would otherwise couple into the signal ground.

Dual Redundant Power Input Logic: The two 24 VDC input terminals are diode-OR’d internally. Each input feeds through a reverse-polarity protection diode before joining the common internal rail. The diode-OR configuration means the switch draws from whichever supply presents the higher voltage, with automatic failover in under 1 ms if one supply drops below the regulation threshold. There is no active power management controller — the failover is purely passive, which eliminates firmware-dependent failure modes in the power path.

Thermal Management: The 1783-US16T is convection-cooled with no moving parts. The ASIC die is thermally coupled to the metal housing via a thermal interface pad, and the housing acts as a heat spreader. At maximum ambient of 60 °C and full 16-port traffic load, the ASIC junction temperature remains within its rated envelope. The absence of a fan is a deliberate design choice for industrial environments where fan bearing failure is a leading cause of unplanned downtime in control panels.

Auto-MDIX Implementation: Each port’s PHY implements Auto-MDIX through a digital signal processing algorithm that detects the polarity and pair assignment of the incoming signal within the first 500 ms of link establishment. This eliminates the need for crossover cables when connecting switch-to-switch or switch-to-NIC, reducing wiring errors during panel assembly and field commissioning.

System Integration Benefits

• Zero-configuration deployment: The switch requires no IP address, no management interface, and no firmware provisioning. It is operational within seconds of power application, reducing commissioning time in time-sensitive machine startups.
• EtherNet/IP implicit I/O compatibility: The hardware CAM table ensures that unicast I/O connection frames are switched directly to the destination port without flooding, preserving bandwidth for other nodes and maintaining the requested packet interval (RPI) of EtherNet/IP connections.
• Deterministic forwarding latency: Store-and-forward latency for a 64-byte frame at 100 Mbps is approximately 5.12 µs plus propagation delay. This fixed, calculable latency allows control engineers to include the switch in their network latency budget with precision.
• Class I Div 2 / ATEX Zone 2 rating: Permits installation inside control panels located in hazardous areas without requiring purged or pressurized enclosures, reducing panel cost and complexity in oil & gas and chemical processing applications.
• Dual-supply redundancy for high-availability panels: When wired to two independent 24 VDC sources (e.g., primary UPS and secondary rectifier), the switch maintains network connectivity through a single power supply failure — a requirement in SIL 2 and SIL 3 safety instrumented system (SIS) architectures.
• DIN rail form factor: 35 mm DIN rail mounting aligns with standard Allen-Bradley I/O, relay, and terminal block hardware, enabling a uniform panel layout and simplifying mechanical design documentation.
• No broadcast amplification risk: The 2,000-entry MAC table is sufficient for all 16 ports to maintain learned unicast entries simultaneously. In a fully populated 16-device segment, the probability of MAC table overflow — which would force the switch to flood all frames as broadcasts — is zero under normal operating conditions.
• Reduced mean time to repair (MTTR): Because the switch has no configuration state, a failed unit can be replaced with a spare in under five minutes without any software reconfiguration, backup restoration, or IP address reassignment. This property is critical in 24/7 manufacturing environments where every minute of downtime has a measurable cost.

Quality Assurance & Global Logistics

Every Allen-Bradley 1783-US16T unit supplied by siemensplc.com is sourced from verified supply channels with full traceability to authorized Rockwell Automation distribution. Prior to dispatch, each unit undergoes a structured pre-shipment inspection protocol: visual examination of housing, label, and connector integrity; serial number cross-reference against known counterfeit databases; and a powered functional test confirming link establishment on all 16 ports and correct LED indication behavior.

Units are packed in anti-static (ESD) bags, cushioned with closed-cell foam, and placed in double-wall corrugated cartons rated for international air freight handling. For orders requiring documentation, we provide a Certificate of Conformance (CoC) and packing list with lot traceability at no additional charge. Country of origin documentation is available for customs clearance in regulated markets.

Logistics operations are based in Xiamen, China, with direct access to Xiamen Gaoqi International Airport and Xiamen Port. Standard air freight transit times are 3–5 business days to Southeast Asia, 5–7 days to Europe, and 5–8 days to North America. Express DHL/FedEx/UPS options are available for urgent requirements. All shipments are tracked end-to-end, with tracking numbers provided within 24 hours of dispatch. Import documentation, including commercial invoice, packing list, and airway bill, is prepared in compliance with destination country customs requirements.

A 12-month warranty covers all units against manufacturing defects. In the event of a warranty claim, replacement units are dispatched within 2 business days of fault confirmation, minimizing production impact.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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