AB 1769-SM2​ 1769-Series DSI Communication Module – Enables DeviceNet Slave Connectivity for Compact I/O Racks, 350 mA @ 5V DC Backplane Powered

Description

Technical Specifications

Main Features and Advantages

The Allen-Bradley 1769-SM2​ provides essential DeviceNet connectivity for the 1769 Compact I/O platform, delivering several key benefits that make it the standard choice for distributed I/O on DeviceNet networks.Distributed remote I/O without a local processor: The primary value of the 1769-SM2​ is that it allows a 1769 rack containing any mix of 1769 digital, analog, ASCII, thermocouple, or specialty modules to function as a standalone DeviceNet slave—no CPU or program is required at the remote location. The DeviceNet master reads the rack’s input data and writes output data across the network, drastically reducing panel cost and complexity for remote stations such as conveyor zones, packaging line infeeds, or process skids located away from the main control cabinet.Three-port DSI RJ45 daisy-chain topology: Equipped with three RJ45 DSI ports, the 1769-SM2​ supports convenient daisy-chaining of multiple DSI devices (such as PowerFlex® drives with DSI ports or additional 1769-SM2-equipped racks) without external T-connectors or repeaters. This simplifies cabling, reduces installation time, and maintains signal integrity through the DeviceNet/DSI multidrop architecture. The RJ45 pinout uses pins 4 (485B/D+) and 5 (485A/D−) for the RS-485 differential pair, consistent with Rockwell’s DSI standard.Flexible I/O mapping and DeviceNet object model: The 1769-SM2​ presents its I/O as standard DeviceNet Explicit and I/O Messages, fully configurable in RSNetWorx for DeviceNet. Input and output sizes are adjustable in increments to match the actual I/O population of the rack, conserving network bandwidth. The module supports both Polled (cyclic) and Change-of-State (COS) I/O modes, and its Identity Object (Class 0x01) reports the exact catalog number and firmware revision for asset management and network discovery.Front-panel rotary MAC ID switches and diagnostics: Setting the DeviceNet node address is tool-free—two thumbwheel switches on the front of the 1769-SM2​ select MAC ID 00–63, eliminating the need to connect a programmer just to assign a node number. Tri-color LEDs (MOD – Module OK, NET – Network OK, and ACT – Network Activity) give immediate visual confirmation of power, network baud lock, node commissioning state, and I/O connection status, greatly accelerating startup and fault isolation during maintenance.Backplane-powered, compact, and rack-compatible: Consuming only 350 mA from the 5 V DC backplane and occupying a single 34 mm slot, the 1769-SM2​ integrates seamlessly into any 1769 chassis used with CompactLogix (L2x/L3x/L4x families) or MicroLogix 1500 expansion systems. Its requirement to be within four slots of a power supply ensures adequate voltage regulation across the backplane, a design constraint shared with other higher-current 1769 modules.Legacy and migration relevance: Although newer distributed I/O strategies favor EtherNet/IP (via 1734 POINT I/O or 1769 Ethernet-enabled processors), the 1769-SM2​ continues to be actively specified for DeviceNet-retained plants—common in automotive, food & beverage, and material handling—where existing DeviceNet infrastructures are maintained. It also serves as a practical MRO item for keeping legacy DeviceNet-based Compact I/O nodes operational without a full network overhaul.

Application Field

The Allen-Bradley 1769-SM2​ is principally applied in Distributed I/O architectures where a DeviceNet network master must scan remote 1769 Compact I/O racks located away from the main controller enclosure. In automotive final-assembly and general assembly lines, the 1769-SM2​ enables zone-based I/O drops—each serving local pushbuttons, indicator stacks, pneumatic valve banks (via 1769-OB16/IB16), and analog sensors (via 1769-IF8/IF16V or 1769-OF4VI)—all tied back to a central ControlLogix or CompactLogix DeviceNet scanner. This approach minimizes home-run wiring, shortens installation time, and localizes troubleshooting to individual zones.Packaging and converting machinery lines often deploy the 1769-SM2​ to place 1769 I/O close to forming heads, glue stations, or print stations that are physically distant from the main panel. The DeviceNet daisy-chain capability of the 1769-SM2​ lets the same trunk also pass through PowerFlex 40/70/700 series drives (which have built-in DSI ports), creating a unified motion + I/O network segment. In water/wastewater treatment plants retaining DeviceNet, the 1769-SM2​ provides remote monitoring of pump station status, local alarm panels, and analog process variables from 1769 analog input modules, all reported to a SCADA-hosted DeviceNet master.For system integrators supporting mixed-vintage plants, the 1769-SM2​ is a key enabler for phased migration: existing 1769 racks with the 1769-SM2​ can remain in service on DeviceNet while the central control platform is upgraded to newer Logix processors, deferring I/O replacement costs. OEM machine builders also embed the 1769-SM2​ in equipment designed for customers who standardize on DeviceNet, allowing their machines to drop onto the customer’s network as a single slave node with configurable I/O maps. Because the 1769-SM2​ requires no programming at the remote rack, commissioning consists only of setting the MAC ID and adding the module to the DeviceNet scanner’s I/O connection list in RSNetWorx—making it accessible even to technicians unfamiliar with Logix programming.