The ABB TB850 3BSC950193R1, also cataloged as the TB850 CEX-Bus Terminator, operates as a dedicated hardware component for providing electrical impedance termination at the physical end-point of a CEX-Bus segment within AC 800M controller architectures.

Model Identification Data

• Full Model Number: TB850 3BSC950193R1

• Base Model: TB850

• Series: AC 800M

• Function: Impedance matching for Controller Extension (CEX) bus

Technical Physical Parameters

Communication Bus Integrity

The module manages the CEX-Bus deterministic network performance by ensuring impedance matching at the terminal node. By maintaining a 120 Ohm load, the unit suppresses signal reflections and standing waves that occur at high-speed data transmission rates. This signal conditioning is required to support the backplane bus communication velocity and ensure that data packet integrity is maintained when the controller rack is configured with multiple expansion or communication interface modules.

Logistics and Scope of Delivery

• One (1) TB850 CEX-Bus Terminator module.

• Integrated screw-down mounting hardware (pre-installed).

• Standard industrial packaging compliant with ESD protection protocols.

Mounting and Field Setup

• Location: Install the terminator exclusively at the final node of the CEX-Bus daisy-chain.

• Mechanical Security: Utilize the integrated screw-fixing mechanism to ensure the DB25P male connector is firmly seated against the chassis to mitigate vibration-induced signal intermittency.

• Environment: Ensure the ambient air temperature remains within the -25 deg C to +70 deg C range; avoid deployment in environments exceeding Pollution Degree 2.

• Grounding: Verify that the cabinet chassis provides a low-impedance path to ground to ensure effective shield termination at the controller level.

Technical FAQs

• Can the TB850 be used in the middle of a CEX-Bus segment? No, the module must only be installed at the physical end of the bus. Placing it mid-segment will cause impedance mismatching and communication errors.

• Is this module hot-swappable? While the physical connector allows for removal, it is recommended to follow site-specific safety procedures for bus-connected hardware to prevent localized signal disturbance.

• What is the function of the 120 Ohm resistor? It matches the characteristic impedance of the CEX-Bus transmission line to prevent signal reflection.

• Does the module require external power? No, it derives its power from the 5 V DC logic supply present on the CEX-Bus.

• Can I use a standard DB25 connector instead of the TB850? No, the TB850 contains specific internal circuitry designed for the AC 800M bus impedance requirements.

• What happens if the TB850 is missing? The open-ended bus will experience signal reflections, which manifest as packet collisions and intermittent CPU-to-interface communication failures.

• Is the module compatible with other controller series? This specific module is engineered for the AC 800M controller family.

• How do I clean the contacts? If oxidation is suspected, use only electronics-grade contact cleaner. Ensure the device is powered down during maintenance.