Allen-Bradley 1746-BAS Industrial Network Interface for SLC 500 Systems

Allen-Bradley 1746-BAS Industrial Network Interface for SLC 500 Systems

The Allen-Bradley 1746-BAS is a BASIC Language Programming Module designed for the SLC 500 modular I/O chassis, delivering a dedicated industrial communication interface that bridges field-level devices with supervisory control and data acquisition systems. In modern smart factory environments, seamless data flow between PLCs, remote I/O, HMIs, SCADA platforms, and upper-level MES systems is not optional — it is the backbone of operational transparency. The 1746-BAS module addresses this need by providing an embedded BASIC interpreter that enables custom communication routines, protocol handling, and real-time data exchange without requiring external gateways or additional middleware.

Engineered for the SLC 500 platform, the 1746-BAS occupies a standard 1746 I/O slot and communicates directly with the SLC 5/03, SLC 5/04, and SLC 5/05 processors via the backplane data table. This tight integration allows the module to read and write directly to integer, binary, and floating-point files, enabling real-time synchronization between field signals and network-layer data. Whether the application involves serial ASCII communication with barcode readers, RS-232 interfacing with weighing terminals, or custom Modbus RTU polling of remote sensors, the 1746-BAS provides the programmable flexibility that fixed-protocol modules cannot match.

Network Communication Table

Connected Automation Data Flow

In a typical SLC 500-based automation architecture, the 1746-BAS module sits at the intersection of the field device layer and the control network, acting as a programmable communication bridge. Consider a production line where a 1746-IB16 digital input module captures discrete signals from proximity sensors and safety interlocks. These signals are processed by the SLC 5/04 processor, which coordinates motion commands to a PowerFlex 40 variable frequency drive via DeviceNet. Simultaneously, the 1746-BAS module runs a BASIC routine that polls a remote Modbus RTU temperature transmitter every 500 milliseconds, writes the result to the SLC data table, and forwards alarm thresholds to a PanelView 550 HMI terminal over RS-232.

As process data accumulates, the SLC 5/05 processor — connected to the plant EtherNet/IP network — makes this data available to a FactoryTalk View SE SCADA server, where operators monitor real-time trends, acknowledge alarms, and generate shift reports. The 1746-BAS module’s BASIC routines can also be configured to communicate with a 1747-SDN DeviceNet Scanner or interface with a 1756-ENBT EtherNet/IP bridge module in a mixed ControlLogix/SLC hybrid architecture, extending the data reach to enterprise-level systems.

For remote I/O expansion, the 1746-BAS works alongside 1746-OB16 digital output modules and 1746-NI4 analog input modules within the same chassis, ensuring that all field signals — whether discrete, analog, or serial — are unified in a single data table accessible to both the local SLC processor and the upstream SCADA or MES platform. In distributed installations, the module’s serial port can be connected to an industrial serial-to-Ethernet converter, enabling remote diagnostics and parameter adjustment without on-site intervention. This capability is particularly valuable in water treatment, oil and gas, and food processing facilities where field panels are located in hazardous or hard-to-reach areas.

Solving Data Isolation in Industrial Sites

One of the most persistent challenges in legacy and hybrid industrial environments is data isolation — the condition where field devices, PLCs, and supervisory systems operate in separate communication silos, preventing real-time visibility and coordinated control. The Allen-Bradley 1746-BAS directly addresses this problem by providing a programmable serial communication layer within the SLC 500 chassis that can be customized to speak virtually any ASCII-based or Modbus RTU protocol.

In facilities where older serial devices — such as legacy weighing scales, barcode scanners, or third-party temperature controllers — cannot be replaced due to cost or process constraints, the 1746-BAS acts as a protocol translator, converting proprietary serial data into SLC 500 data table values that are immediately accessible to the plant SCADA system. This eliminates the need for standalone protocol converters or OPC servers running on fragile PC hardware, reducing both cost and single-point-of-failure risk.

For production line transparency, the 1746-BAS enables real-time data logging by periodically writing process values to the SLC data table, which are then polled by FactoryTalk Historian or a third-party SCADA historian. Alarm conditions detected by the BASIC routine — such as a sensor value exceeding a defined threshold — can trigger immediate notifications to the HMI or initiate an automated response in the SLC ladder logic program. Remote diagnostics are supported through the module’s serial port, allowing maintenance engineers to connect a laptop running RSLinx Classic or a terminal emulator to interrogate the BASIC program status and data table values without interrupting production.

System expansion is straightforward: additional 1746-BAS modules can be installed in the same or adjacent SLC 500 chassis slots, each handling a separate serial communication channel. This modular approach allows the communication infrastructure to grow alongside the production system, supporting new devices and protocols as the smart factory evolves — without requiring a complete control system redesign.

Industrial Connectivity FAQ

Q1: What communication protocols does the Allen-Bradley 1746-BAS support?
The 1746-BAS supports any ASCII-based serial protocol and Modbus RTU through user-written BASIC programs. It is compatible with RS-232C, RS-422, and RS-485 physical layers, making it adaptable to a wide range of field devices including sensors, barcode readers, weighing terminals, and third-party controllers. Protocol-specific timing, framing, and error-handling logic is implemented directly in the BASIC program, giving engineers full control over communication behavior.

Q2: How does the 1746-BAS integrate with SCADA and HMI systems?
The module writes data directly to the SLC 500 integer and floating-point data tables via the backplane. These values are immediately accessible to the host SLC processor, which can forward them to a FactoryTalk View SE or PanelView HMI over DH+, EtherNet/IP (via SLC 5/05), or DF1. SCADA systems connected to the SLC network via RSLinx or OPC-DA/UA servers can poll these data table values in real time, enabling live dashboards, trend logging, and alarm management without additional hardware.

Q3: Is the 1746-BAS suitable for network expansion in existing SLC 500 installations?
Yes. The 1746-BAS occupies a standard 1746 I/O slot and requires no special chassis or power supply modifications. Multiple modules can be installed in the same chassis, each managing an independent serial communication channel. This makes it an ideal solution for expanding communication capacity in existing SLC 500 systems without replacing the controller or chassis infrastructure.

Q4: What quality assurance and warranty coverage is provided?
Every Allen-Bradley 1746-BAS unit supplied by ZYPLC undergoes functional testing prior to shipment, including backplane communication verification and serial port integrity checks. All units are covered by a 12-month warranty against manufacturing defects and communication failures. In-stock units are available for same-day or next-day dispatch via DHL or FedEx international express, with full tracking provided. For volume orders or urgent requirements, contact our team directly for lead time confirmation and technical support.

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