Product Overview

The Allen-Bradley 1771-ASB functions as the primary communication link for distributed control topologies within the Rockwell Automation PLC-5 architecture. This network interface card populates the leftmost slot of a remote 1771 I/O chassis, establishing a high-speed data connection back to a central PLC-5 processor over the Allen-Bradley Remote I/O (RIO) network. The 1771-ASB scans peripheral discrete and analog I/O modules plugged into its local backplane, packs the field signals into standard corporate data blocks, and transmits this data upstream in real time. Industrial production complexes, packaging facilities, and process plants deploy this module to eliminate expensive multi-conductor home-run wiring by decentralizing I/O chassis directly next to field instruments.

Technical Specifications

Engineering Advantages

Comprehensive RIO Addressing Matrix Maximizes Data Density

The 1771-ASB offers highly flexible memory mapping through full rack, 1/2 rack, and 1/4 rack logical addressing schemes. This granular block allocation allows engineering teams to optimize the PLC-5 data table based on the exact density of the installed hardware. By mapping high-density 32-point digital modules or complex multi-channel analog modules into specific, isolated group sectors, the adapter ensures that the central controller processes field variables efficiently without wasting logical network addresses on empty slots.

Selectable High-Speed Baud Rates Adapt to Expansive Distances

Signal attenuation and cable length limits present severe obstacles when routing communication lines across sprawling factory floors. The 1771-ASB provides three selectable hardware baud rates (57.6 kbps, 115.2 kbps, and 230.4 kbps) to balance data throughput against physical network span. Engineers running shorter links select 230.4 kbps to prioritize sub-millisecond data updates, while facilities extending networks across large physical spaces drop the transmission frequency down to 57.6 kbps to guarantee clean, uncorrupted signaling over thousands of feet of standard blue hose twinaxial cable.

Standardized Leftmost Slot Seating Secures Remote Backplane Sync

To maintain strict data synchronization and prevent logic collision over the internal chassis bus, the 1771-ASB mounts exclusively in the leftmost hardware slot of any 1771 enclosure (such as the 1771-A4B). This physical location grants the adapter absolute control over the chassis backplane timing cycles. The module acts as the local traffic manager, supplying continuous data arbitration to peripheral input and output cards, while pulling 1.2 Amps of regulated 5V logic power safely from the chassis power source without requiring auxiliary line drops.

FAQs

• What hardware adjustments must technicians configure before installing a brand new 1771-ASB?

  Before inserting the 1771-ASB into the leftmost slot of the remote chassis, technicians must adjust the onboard hardware DIP switch blocks. These physical switches establish the unique logical rack number, the primary network baud rate (57.6, 115.2, or 230.4 kbps), and the specific I/O addressing mode (2-slot, 1-slot, or 1/2-slot) assigned to that station. Mismatched switch settings will cause network communication errors and trigger an immediate I/O adapter fault status at the central PLC-5 processor.

• Can the 1771-ASB communicate directly across standard modern EtherNet/IP networks?

  No. The 1771-ASB interfaces strictly with the proprietary Allen-Bradley Remote I/O (RIO) network protocol and uses blue hose twinaxial cabling. It does not contain an RJ45 port or possess native TCP/IP routing logic. If a facility requires integration into a modern Ethernet/IP control system (such as ControlLogix), you must utilize specialized network conversion gateways or replace the legacy RIO adapter with a contemporary network bridge module.

• How do the diagnostic indicators on the front faceplate assist during network troubleshooting?

  The front faceplate of the 1771-ASB features a dedicated stack of diagnostic status LEDs that provide real-time network visibility. Under normal operating conditions, the indicators confirm active backplane scanning and valid RIO network communication. If the blue hose line breaks, an incorrect baud rate matches, or a duplicate rack address occurs on the link, the adapter alters the LED pattern immediately, identifying whether the failure resides in the local chassis backplane or along the incoming upstream network path.