Product Description:

The BC9120 is a compact Bus Terminal Controller built by Beckhoff for the BC Bus Terminals series. It combines an embedded PLC and an Ethernet fieldbus coupler so slice I/O can be controlled directly from the station. Within an automation cell, the unit gathers decentralized digital or analog signals and transmits them to supervisory computers, making it a small-footprint node for distributed machine control. Because the user program executes locally, reaction times stay predictable even when higher-level networks are saturated.

During runtime, the controller maps 2 kB of address space to its input image, while a matching 2 kB segment is reserved for outputs. A further 4 kB flag area stores Boolean and byte variables that require high-speed access but not retention. Communication is handled through the Ethernet interface, permitting ADS over TCP/IP as well as conventional fieldbus telegrams. Task processing is organized in a single cycle because the controller supports only 1 PLC task, so all user code must execute within that interval. Up to 2 kB of retain memory preserves counters and recipe data across power cycles. Status bits, watchdogs, and forcing functions follow Beckhoff diagnostic conventions, which helps keep controller behavior consistent across similar systems.

The station ships with the default AMS Net ID set to 172.16.23.[DIP-Switch].1.1, and changing the rotary switches on the front panel updates this identifier to create a unique network address. For serial access or bootstrap operation, revision B0 or newer is required, while Ethernet access needs TwinCAT 2.10 Build 1322 and serial ADS development needs TwinCAT 2.9 Build 1010 or newer. These version levels allow variable lists, online changes, and startup parameters to exchange correctly with the development environment.