Allen-Bradley 1771-SN
Allen-Bradley 1771-SN
Allen-Bradley 1771-SN
Allen-Bradley 1771-SN
Allen-Bradley 1771-SN
Allen-Bradley 1771-SN
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1771-SN

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The Allen-Bradley 1771-SN is a Sub I/O scanner module designed for remote I/O communication within PLC-2 compatible systems. It manages data transfer between PLC processors and multiple remote I/O chassis through a structured block-transfer mechanism.
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Technical specifications for 1771-SN

  • Manufacturer:
    Allen-Bradley
  • Part Number:
    1771-SN
  • Product Family:
    PLC-5
  • Product Type:
    Sub I/O Scanner Module
  • Module Location:
    1771-A1B thru -A4B or later l/O chassis and 1771-AM1and-AM2l/O chassis
  • Data Transmission Rate:
    10,000 cable-feet at 57.6k bits/s; 5,000cable-feet at 115.2k bits/s
  • Interconnect Cable:
    1770-CD or equivalent (refer to the Approved Cable Vendor List, pub.no.lCCG-2.2)
  • Backplane Current:
    1.2A
  • Power Dissipation:
    7W maximum @1.2A
  • Thermal Dissipation:
    24 BTU maximum @1.2A
  • Keying:
    Between 2 and 4, Between 24 and 26.
  • Operating Temperature:
    0°C to 60°C (32°F to 140°F)
  • Storage Temperature:
    -40°C to 85°C (-40°F to 185°F)
  • Relative Humidity:
    5% to 95% (without condensation)
  • System:
    Supports PLC-2 rack addresses 1 thru 7; Supports up to 16 total adapters; Does not support complementary I/O.
  • Weight:
    0.88 kg
  • Estimated shipping dimensions:
    2.8x14.5x26cm
  • Tariff Code:
    9004909000
  • Country of origin:
    USA
  • Place of shipment:
    Xiamen, Fujian, China
By purchasing this item, you agree to the Terms & Conditions, ApterPower is not an authorized distributor for listed manufacturers or tradenames and therefore the manufacturer's warranty does not apply. All our products come with ApterPower's 1-year warranty.

More Information

Overview Manuals Specifications Application Scenarios Configuration Compliance

Features:

  • Provides structured remote I/O scanning and data exchange through PLC-2 compatible architecture.
  • Supports configurable fault handling with independent and dependent control modes across multiple I/O chassis.
  • Enables long-distance communication with defined transmission rates and structured block-transfer data mapping.
The Allen-Bradley 1771-SN module is designed for remote I/O communication within rack-based PLC systems, ensuring coordinated data exchange between processors and distributed I/O chassis. The Allen-Bradley 1771-SN operates within defined chassis compatibility and supports structured rack addressing for system organization. Its communication framework is based on block-transfer instructions that ensure consistent data movement across the control network.

In system operation, the 1771-SN supports multiple adapter devices while maintaining synchronized communication rates across the entire remote I/O link. The Allen-Bradley 1771-SN manages both input and output data through predefined word structures, ensuring that each rack and group is mapped correctly within the PLC data file. Reserved word areas provide system-level fault and status information for monitoring and diagnostics.

From an industrial integration perspective, the Allen-Bradley 1771-SN enables flexible configuration of fault response behavior depending on system requirements. The module supports independent operation between racks or coordinated fault response in dependent mode. Through structured block-transfer handling, the 1771-SN ensures consistent communication behavior across distributed I/O architectures, supporting stable PLC system operation.

The 1771-SN Allen-Bradley Sub I/O Scanner Module may still be available for purchase and support from Apter Power beyond End-Of-Life (EOL) by the manufacturer (OEM).
Allen-Bradley 1771-SN Sub I/O Scanner Module Manuals,Datasheets,Link Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.
Allen-Bradley 1771-SN Sub I/O Scanner Module Specs

General

  • Manufacturer Allen-Bradley
  • Model 1771-SN
  • Condition New Original ready stock
  • Product Family 1771-AS,1771-A4,1771-A4E
Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.
  • Distributed Control: Used to extend the I/O control range of PLC-5 or similar control systems to remote locations, managing equipment distributed across different locations within a factory through a single remote I/O link.
  • System Expansion: When backplane slots are insufficient, add up to 896 remote digital I/O points via the 1771-SN for large-scale system expansion.
  • Remote Monitoring: Communicate with remote 1771-ASB adapters over distances up to 10,000 feet (approximately 3048 meters) to collect field sensor signals and drive actuators.
  • Device Integration: Integrate different types of 1771 digital or analog I/O modules into a unified remote link, reducing field cabling costs and increasing system maintenance flexibility.
  • DIP Switch Settings: The communication rate (e.g., 57.6kbps or 115.2kbps) and fault control mode can be adjusted via switch groups 0 and 1 at the cutout on the left side of the module.
  • Rack Addressing: Configure Sub I/O scanners in the PLC program, supporting up to 7 logical rack addresses (in 1/4 rack increments), and connecting up to 16 remote adapters.
  • Ladder Diagram Programming: Use BTW (Block Transfer Write) instructions to transfer configuration data and output mappings to the module, and use BTR (Block Transfer Read) instructions to read remote input status.
  • Hardware Installation: Insert the module into any slot of the 1771 general-purpose I/O rack (except the first slot on the left, which is reserved for a processor or adapter), and connect the 1770-CD remote I/O cable.
  • Environmental Rating: This equipment is suitable for industrial environments of pollution level 2 as defined by IEC 60664-1, and applications in overvoltage category II.
  • Electromagnetic Compatibility (EMC): Complies with Council Directive 89/336/EEC, and is suitable for industrial environments under EN 50081-2 and EN 50082-2 standards.
  • Safety Certification: As an "open" device, it must be installed in a properly designed cabinet to prevent personnel from contacting live parts and to meet specific environmental protection requirements.
  • Low Voltage Directive: Meets the requirements and tests for programmable controller devices according to EN 61131-2, and complies with Council Directive 73/23/EEC.
Description
The Allen-Bradley 1771-SN Sub I/O scanner module is engineered for installation in 1771-A1B through A4B or later I/O chassis, as well as 1771-AM1 and AM2 chassis. It operates as a central interface for remote I/O links, coordinating communication between the processor and distributed I/O adapters. The 1771-SN ensures structured integration within PLC-2 compatible rack-based systems. It supports up to 16 adapters across a defined network architecture.

In terms of communication capability, the 1771-SN supports transmission distances of up to 10,000 cable-feet at 57.6 kbps and 5,000 cable-feet at 115.2 kbps. It uses 1770-CD or equivalent interconnect cable as specified in approved documentation. The module operates with a backplane current of 1.2A, a maximum power dissipation of 7W, and thermal dissipation up to 24 BTU. Operating temperature ranges from 0°C to 60°C, while storage conditions extend from -40°C to 85°C, with 5% to 95% relative humidity without condensation.

The 1771-SN Scanner requires synchronized communication rates across all connected adapter devices on the remote I/O link. It supports PLC-2 rack addresses from 1 to 7 and does not support complementary I/O. Each remote chassis is configured with independent or dependent fault control settings, allowing output behavior to be defined in case of communication or system faults. Rack assignment consistency and switch configuration determine how faults are isolated or propagated across connected chassis.

Fault handling within the Allen-Bradley 1771-SN includes independent fault control, where loss of communication in one chassis does not affect others with different rack numbers. In dependent mode, communication loss can influence output states across multiple chassis based on last-state switch configuration. The module automatically clears fault bits after correction, although a power cycle is required to reset the fault counter. A fault table can also be generated in the block-transfer read file for detailed diagnostics.

Data handling is managed through block-transfer read and write instructions, with file length calculated as 8 + (8 × highest rack number). The first eight words are reserved for system and fault data, while subsequent words represent I/O data from remote racks. The 1771-SN uses structured mapping where each rack and group corresponds to specific word positions. Status words track serial communication faults, while both input and output data are transferred between PLC and remote I/O chassis through defined read/write blocks.
Revisions

Revision Part #

Also known as

1771-SN Ser A
1771-SN/A, Series A, Rev A
1771-SN Ser B
1771-SN/B, Series B, Rev B
Alternative Names
1771-AS 1771-ASB 1771-A4 1771-A4E 1771SN 177I-SN 177ISN I771-SN I771SN
Technical notes
The Allen-Bradley 1771-SN Sub I/O scanner module is installed in 1771-A1B to A4B or 1771-AM1/AM2 chassis, operating with 1.2A backplane current, 7W maximum power dissipation, and 24 BTU thermal dissipation; it supports 10,000 cable-feet at 57.6 kbps and 5,000 cable-feet at 115.2 kbps using 1770-CD cable, functions within 0°C to 60°C operating temperature, -40°C to 85°C storage range, and 5–95% non-condensing humidity, and supports PLC-2 rack addresses 1–7 with block-transfer read/write data structure defined as 8 + (8 × highest rack number) including reserved words for fault and status handling.
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FAQS

The following is a list of questions commonly asked by our customers. Please contact us if you have a question about our process that is not answered below.
Why must all devices share the same communication rate in a 1771-SN system?
Because mismatched communication rates can disrupt synchronization on the remote I/O link.
How does the Allen-Bradley 1771-SN handle fault conditions?
It supports independent and dependent fault control depending on rack configuration and switch settings.
What cable type is used with the 1771-SN Scanner module?
It uses 1770-CD or equivalent interconnect cable as defined in approved vendor documentation.
How many adapter devices can be supported by the 1771-SN system?
It supports up to 16 total adapters within the remote I/O network.

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