1769-SM2 — Compact I/O to DSI/Modbus Communication Module

The 1769-SM2 is a communication module for the Compact I/O platform that bridges a controller to small-class AC drives over Drive Serial Interface (DSI) or to Modbus RTU slave devices on the same RS-485 wiring. It occupies a single chassis slot and gives the controller direct read/write access to drive parameters and control words without requiring a separate network adapter or proprietary drive-specific gateway.

Specifications

Parameter	Value
Part Number	1769-SM2
Platform	Compact I/O (1769)
Protocols	DSI, Modbus RTU
Connection Channels	3 (RJ45)
Max Drives per Channel	5 (multi-drive mode), up to 15 total
Max Cable Distance to Drive	10 m
Max Twisted-Pair Network Distance	1219 m
Backplane Current (5V)	350 mA
Power Supply Distance Rating	4 (modules from power supply)
Operating Temperature	-10°C to 50°C

Bridging a PLC to a Drive Without a Network Card

Many small AC drives include a DSI port as their standard control interface — a simple serial connection that handles parameter access, fault status, and run commands without requiring an Ethernet or fieldbus card on the drive itself. The 1769-SM2 sits on the controller's Compact I/O bus and translates that DSI traffic into data the controller program can read and write directly, treating the connected drives almost like extended I/O. In multi-drive mode, a single module manages up to five drives per channel across its three channels, covering a meaningful number of small drives from one chassis slot.

For non-DSI devices, the same module switches to Modbus RTU master operation, polling third-party drives, meters, or instruments with Modbus RTU slave interfaces over the same RS-485 wiring. This dual-protocol capability is useful in mixed-vendor panels where some devices speak DSI natively and others only support Modbus.

FAQ

Q: Can the 1769-SM2 control drives over Ethernet instead of serial?

No. This module is specifically a serial (DSI/Modbus RTU) interface. For Ethernet-based drive communication, a drive with a built-in or add-on Ethernet communication card is required instead.

Q: How far away from the controller's power supply can this module be installed?

Up to four module slots away, per its power supply distance rating — placing it beyond that distance risks unreliable backplane voltage at the module.

Q: Does switching between single-drive and multi-drive mode require any special procedure?

Switching configuration modes is done through the module's setup in the programming software. Some operations, such as firmware updates in multi-drive mode, require switching to single-drive mode first.

Q: Can this module be used as remote I/O rather than locally with the controller?

Yes. It can function as local expansion I/O directly on a controller's bus, or as remote I/O behind a compatible network adapter, depending on the system architecture.

1769-SM2 New 1769SM2 Ser A Compact I/O DSI Modbus Rtu Communication Module