Product Description:

The X20BB57 is a modular bus base produced by B & R Automation for the X20 Fieldbus Input Output Modules series. Acting as the mechanical and electrical backbone of an I/O slice, it anchors additional function modules and exposes the communication channels that tie the slice to the controller. Within an automation cell, it provides the physical layer that distributes power, establishes communication, and simplifies cabinet wiring.

The base carries an integrated fieldbus transceiver for CAN bus, enabling deterministic messaging to the PLC without external gateways. A second onboard port exposes RS232, allowing service access or communication with legacy devices over the same slice. These two channels make up the module’s 2 communication interfaces. Power and identification signals arrive through the keyed backplane at 24 VDC, helping prevent incorrect insertion of modules that run on other potentials. All user conductors enter through the front where 12 terminal pins accept sensors, actuators, and shield connections, and the push-in spring cages permit tool-free wiring while maintaining constant contact force. The housing snaps onto a top-hat rail, providing mechanical support and allowing easy removal when the installation layout changes.

Identification is handled by the embedded parameter chip, which stores module type and calibration data so the CPU can automatically detect the slice. Protective earth continuity is maintained because the ground reference is carried via top-hat rail, eliminating separate grounding straps. As a bus base, the unit routes the internal power bus, distributes the serial and fieldbus lines, and locks the next I/O module into precise pitch. Combined with the dedicated mounting rail, this arrangement reduces panel depth and keeps wiring orderly when additional digital or analog points are added.