Allen‑Bradley 1746-BAS BASIC Module for SLC 500 – ASCII/Serial Integration and Offloaded Logic

The Allen‑Bradley 1746-BAS is a BASIC language module for the SLC 500 platform designed to handle ASCII devices and custom logic without overloading the main CPU. From my experience, it’s a practical way to integrate barcode scanners, weigh scales, printers, and other serial peripherals directly into an SLC 500 system—especially where simple protocol parsing or string handling is needed. One thing I appreciate is how it offloads math and data manipulation, so scan times on the main controller typically stay consistent even as serial traffic grows.

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Key Features

• BASIC Language Runtime – Write and execute BASIC programs inside the module to parse ASCII, perform math, and handle custom routines.
• Serial/ASCII Connectivity – Typically used to connect barcode readers, label printers, weigh scales, or legacy instruments that talk ASCII.
• Offloads CPU Tasks – Moves string handling and protocol parsing off the SLC CPU, which in many cases helps keep ladder scan times stable.
• Tight SLC Integration – Exchanges data with the controller via M0/M1 files and status commands for reliable handshaking.
• Flexible Data Handling – Floating‑point math, buffers, and string functions make custom data formatting straightforward.
• Development via Serial Terminal – Program and debug over a serial terminal session; simple to test line‑by‑line logic.
• Standard 1746 Form Factor – Installs in a single slot of a 1746 chassis alongside your existing SLC I/O and specialty cards.

Technical Specifications

Application Fields

Typically deployed wherever an SLC 500 needs to talk to ASCII or proprietary serial devices. You might notice it’s especially helpful in:

• Discrete manufacturing: barcode/2D code scanning for WIP tracking and label printing
• Food & beverage: weigh scale capture and recipe data formatting to printers
• Warehouse & logistics: direct serial printer control and scanner aggregation
• Process skids: parsing ASCII strings from analyzers or lab instruments to SLC tags
• Legacy integration: bridging older serial‑only devices into modern SCADA/HMI via the SLC

Advantages & Value

• Reliability – Mature, well‑documented module with predictable behavior in SLC environments.
• Compatibility – Fits standard 1746 chassis and works alongside existing SLC I/O with minimal program changes.
• Cost Savings – Eliminates separate protocol gateways when the requirement is straightforward ASCII parsing or printing.
• Technical Efficiency – Offloads heavy string handling so the main CPU scan typically remains stable under load.

A maintenance supervisor recently shared that adding a 1746‑BAS for printer control “cleaned up” their ladder program—fewer rungs, fewer timeouts, and far easier troubleshooting when a printer cable goes bad.

Installation & Maintenance

• Panel/Cabinet: Mount the 1746 chassis in a clean, dry, ventilated cabinet; maintain ambient 0–60 °C with adequate airflow.
• Slotting: Install the 1746‑BAS in any available single slot; verify keying and ensure the PSU capacity is sufficient for the added backplane load.
• Wiring: Use shielded serial cables for longer runs; tie shields at one end to reduce ground loops. Keep serial and power wiring separated.
• Program Integration: Exchange data through M0/M1 files; implement simple status bits/handshake to avoid buffer overruns.
• Maintenance: Periodically check connectors for looseness/oxidation; back up BASIC programs. If using battery‑backed storage, replace batteries on the recommended interval.
• Firmware/Tools: Keep your terminal/emulation tools consistent across updates; label serial settings (baud, parity, stop bits) inside the panel door for quick service.

Quality & Certifications

• Certifications: CE and UL/cUL (typical for SLC 500 modules); CSA availability depending on series
• Manufacturing standards consistent with Rockwell Automation quality systems
• Warranty: 365 days