Configured for high-capacity I/O scanning, message buffer processing, and serial interface translation in PLC-3 rack structures, the Allen-Bradley 1775-S4B (1775-S4B I/O Scanner Message Handling Module) provides direct physical/electrical execution.

Architectural Designation & System Integration

The catalog identifier 1775-S4B specifies an I/O scanner and message handling module designed for PLC-3 control architectures. The module establishes 4 dedicated remote I/O communication channels paired with 1 serial RS-232-C port, handling up to 2048 discrete inputs and 2048 discrete outputs with an internal 16-word message buffer.

Operational Parameters & Ratings

Deterministic Communications & Network Integration

The module optimizes backplane bus communication velocity across the rack assembly, providing synchronized message routing to central processors. Integrated diagnostic monitoring verifies firmware flash compatibility across connected nodes, ensuring low-latency frame parsing and predictable execution when managing complex I/O density scaling profiles.

Package Component Checklist

• 1 x Allen-Bradley 1775-S4B I/O Scanner Message Handling Module
• 1 x Protective Static Shield Packaging Envelope
• 1 x System Installation and Wiring Guide

Field Cabinet Installation Guidelines

• Chassis Alignment: Insert the module firmly into its designated chassis slot with power isolated to protect internal backplane connectors.
• Serial Interface Wiring: Connect RS-232-C serial cables using shielded twisted-pair wiring with low capacitance ratings to maintain baud rate integrity.
• Remote I/O Line Routing: Run 4 independent remote I/O communication channels in isolated conduits separate from high-voltage AC power lines.
• Earthing and Shielding: Secure all cable shields to the main panel earthing bar at a single point to prevent ground loop currents across communication lines.

Frequently Asked Questions

• What is the backplane current draw for the 1775-S4B module?

  The module draws 2.7 A from the 5 VDC chassis backplane supply rail during normal execution.

• What maximum I/O count can be managed by the 1775-S4B?

  The module handles a maximum capacity of 2048 discrete inputs and 2048 discrete outputs across its channels.

• What baud rates are supported on the remote I/O channels?

  The 4 remote I/O communication ports support selectable transfer rates of 57.6 kbaud or 115.2 kbaud.

• What is the typical I/O scan response time for this module?

  The hardware completes an internal I/O scan cycle within a timing window of 5.5 ms to 6.5 ms.

• What size is the integrated message buffer?

  The module incorporates an internal hardware buffer capacity of 16 words for serial message handling.

• What fuse protection is required for line supply power?

  The internal power circuit uses a 2 A fuse for 115 V operation or a 1 A fuse for 230 V operation.

• Does the module support live removal from the rack backplane?

  No, backplane power must be completely isolated prior to inserting or extracting the module.

• What isolation rating is provided between power and logic circuits?

  The integrated power section provides internal galvanic isolation rated up to 1500 VAC.