Allen-Bradley 1747-DCM Direct Communication Module

Configured for Remote I/O data exchange in SLC 500 backplane architectures, the Allen-Bradley 1747-DCM (1747-DCM Direct Communication Module) provides direct physical and electrical execution of RIO link interfacing between SLC 500 controllers and supervisory network segments within Rockwell Automation SLC 500 systems. The module operates as a backplane-mounted communication interface supporting deterministic RIO transmission without local logic execution.

Suffix Breakdown & Model Matrix

No suffix segmentation is defined for 1747-DCM. The module is a single-configuration communication unit within the SLC 500 product line.

Hardware Specifications

Backplane Bus Communication and RIO Deterministic Link Architecture

Within Rockwell Automation SLC 500 backplane systems, the 1747-DCM implements a dedicated Remote I/O communication layer that operates independently of local CPU scan execution. The module consumes 360 mA at 5 VDC from the chassis backplane, establishing a deterministic data exchange channel through RIO protocol framing.

The communication path supports selectable baud rates from 57.6 Kbaud to 230.4 Kbaud, with signal integrity governed by Belden 9463 cabling impedance matching and termination resistors of 82 Ohm or 150 Ohm depending on network topology length. The module does not perform signal buffering beyond protocol framing, ensuring direct mapping between PLC memory image and remote I/O rack states.

Backplane coupling is fixed-slot dependent, and module behavior is synchronized with SLC 500 scan cycle timing, where RIO updates are exchanged in cyclic deterministic frames rather than event-driven interrupts.

Frequently Asked Questions (FAQ)

Q: Does the 1747-DCM execute local control logic?
A: No. The module only handles RIO communication framing and does not execute ladder logic or internal processing.

Q: What is the backplane current requirement?
A: The module draws 360 mA at 5 VDC from the SLC 500 chassis backplane.

Q: Can the transmission rate be dynamically changed during operation?
A: No. Baud rate selection (57.6 Kbaud to 230.4 Kbaud) is configured prior to runtime and remains fixed during operation.

Field Installation Guidelines

The module shall be installed in any available slot of an SLC 500 chassis with power removed prior to insertion. Backplane connectors must be fully seated to ensure correct 5 VDC and data bus alignment.

RIO cabling must use Belden 9463 or equivalent shielded twisted pair with correct termination (82 Ohm or 150 Ohm) at network endpoints. Cable routing shall avoid parallel runs with high-voltage conductors to minimize induced noise on RIO differential lines.

Shield grounding shall be implemented at a single reference point to prevent ground loop currents across multi-drop RIO segments.