1771-SN | Allen-BradleyPLC-5 Sub-I/O Scanner Module

Product Overview

The Allen-Bradley 1771-SN functions as a Sub-I/O Scanner module within the Universal 1771 I/O platform. It extends the control capabilities of a PLC-5 processor by managing a dedicated Universal Remote I/O (RIO) link. This module acts as an intelligent interface, scanning remote I/O chassis and discrete devices to update the processor's data table. We supply this unit as 100% Brand New and Original, ensuring your legacy control architecture maintains peak timing accuracy and communication integrity.

Technical Specifications

The 1771-SN utilizes the PLC-5 backplane to execute high-speed block transfers while maintaining a minimal power footprint.

• Manufacturer: Allen-Bradley / Rockwell Automation

• Product Line: PLC-5 (1771 I/O)

• Module Type: Sub-I/O Scanner Module

• Communication Protocol: Universal Remote I/O (RIO)

• Processor Communication: Block-Transfer via PLC-5 Backplane

• Slot Occupancy: 1 Slot

• Backplane Current: 0.2 Amperes

• Wiring Arm: 1771-WN

• Typical DC Signal Delay: 3 ms (On) / 30 ms (Off)

• Typical AC Signal Delay: 11 ms (On) / 29 ms (Off)

• Weight: 1.94 lbs (0.88 kg)

Engineering Advantages

• Distributed Architecture Expansion: The 1771-SN enables the processor to control I/O located thousands of feet away from the main chassis. This capability reduces local wiring costs and allows for the decentralization of control cabinets across large manufacturing floors.

• Efficient Backplane Utilization: With a low current draw of only 0.2 Amperes, this module places minimal thermal and electrical stress on the 1771 power supply. This efficiency allows engineers to populate more communication and I/O modules within a single rack without exceeding power limits.

• High-Speed Block Transfers: The module utilizes Block-Transfer instructions to move large arrays of data between the scanner and the PLC-5 processor. This method ensures that the controller receives comprehensive diagnostic and status data without consuming multiple scan cycles for individual bit updates.

• Hardware Compatibility Protection: The use of the standard 1771-WN wiring arm ensures secure field connections. Furthermore, the mechanical keying of the 1771 chassis prevents the accidental insertion of non-compatible modules into the scanner slot, safeguarding the system from electrical mismatch and hardware damage.

FAQs

• How does the 1771-SN communicate with the PLC-5 processor? The module uses Block-Transfer Read (BTR) and Block-Transfer Write (BTW) instructions. The processor initiates these transfers to exchange I/O image data and status information with the scanner's internal memory.

• Does this module require a specific software configuration? Yes. You must configure the Remote I/O scan list within the PLC-5 programming software (such as RSLogix 5). You define the rack addresses, group starting points, and I/O sizes to ensure the scanner correctly identifies all remote adapters on the link.

• Can the 1771-SN be used in a remote chassis? No. The 1771-SN must reside in the same local chassis as the PLC-5 processor (or in an extended local chassis) because it functions as a scanner, not an adapter. It manages the link that remote adapters connect to.

• What is the significance of the signal delay specifications? The delay specifications (e.g., 3 ms for DC On) represent the time the module takes to process signal transitions. Understanding these values is critical for engineers designing high-speed interlocking or safety-related logic where millisecond-level precision determines system safety.