1769-SM2 Allen-Bradley DSI Modbus Communication Module
Manufacturer: Allen Bradley
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Part Number: 1769-SM2
Condition：New with Original Package
Product Type: Communication Modules
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Country of Origin: USA
Payment:T/T, Western Union
Shipping port: Xiamen
Warranty: 12 months
Allen-Bradley 1769-SM2 CompactLogix Communication Module
The Allen-Bradley 1769-SM2 SER A, also cataloged as the 1769-SM2 Communication Module, operates as a dedicated hardware component for serial data communication transmission within CompactLogix and MicroLogix 1500 controller networks. The device functions as a specialized gateway, converting backplane signals into Drive Serial Interface (DSI) or Modbus RTU protocol sequences. By executing direct physical link handling, the module establishes connectivity between processing units and up to 15 PowerFlex 4-class or 7-class variable frequency drives without requiring external protocol converters or software bridges.
Hardware Specifications
| Parameter | Specification |
|---|---|
| Model | 1769-SM2 SER A |
| Brand | Allen-Bradley |
| Origin | Mexico |
| Weight | 0.38 lbs (0.17 kg) |
| Dimensions | Standard CompactLogix 1769 single-slot module width |
| Operating Temp | -10 to 50 deg C |
| Power Consumption | 350 mA at 5 VDC, 0 mA at 24 VDC |
| Network Type | DSI, Modbus RTU |
| Number of Channels | 3 independent serial channels |
| Channel Connector Type | RJ45 connectors |
| DSI Baud Rate | Fixed at 19,200 bps |
| Modbus Baud Rates | 300, 600, 1200, 2400, 4800, 9600, 19,200, 38,400 bps |
| Power Supply Distance Rating | Max 4 modules from power supply |
| Operating Modes | Single Mode (1 drive) and Multi-Drive Mode (up to 5 drives per channel) |
Backplane Bus Communication Velocity and Firmware Flash Compatibility
The system bus interfaces directly with the host controller backplane to maintain the overall backplane bus communication velocity needed for deterministic control timing. Electrical execution requires 350 mA at 5 VDC drawn completely from the Compact I/O power supply rail, leaving the 24 VDC track unused. To prevent communication timeouts and signal attenuation on the local bus, technicians must observe the power supply distance rating, which limits installation to within 4 module slots of the system power source. Network performance dependably aligns with firmware flash compatibility protocols across CompactLogix platforms, enabling operators to flash system updates exclusively via ControlFLASH software over the active 1769 backplane interface.
Frequently Asked Questions
Q: Can this communication module be extracted or replaced while the 1769 backplane is powered?
A: No. The module does not support hot-swapping or Removal and Insertion Under Power (RIUP). Breaking the backplane connections while the 5 VDC power supply rail is energized can cause electrical damage to the internal bus transceivers and immediately fault the host controller.
Q: How do the network distance limits change based on the drive topology used?
A: When connecting to a single drive in Single Mode, the physical cable length is limited to a maximum of 10 m. In Multi-Drive configurations using RS485 distribution techniques, the total combined network length across the daisy-chained layout can reach a maximum limit of 1219 m.
Field Installation Guidelines
- Bus Connection and Locking Sequence: Align the side tongue-and-groove tracks to slide the module into the adjacent 1769 slot. Push the upper and lower bus levers forward to complete the physical backplane connections. Both mechanical latches must lock fully into position before applying system power.
- Chassis Mounting and Grounding: Mount the module onto an EN 50022 compliant 35 mm DIN rail, or use two #8 or M4 panhead screws to secure the unit directly to the control panel sub-plate. Maintain proper spacing to accommodate the 3 front-facing RJ45 channel connectors.
- Serial Cable Shielding and Routing: Route all DSI and Modbus RTU communications through high-quality shielded twisted-pair copper cables (22 to 14 AWG solid or 22 to 16 AWG stranded). Ground the cable shield at a single termination point on the enclosure chassis, keeping communication lines physically isolated from high-voltage AC motor lines to avoid electromagnetic interference.