Siemens SIMATIC S5 6ES5928-3UB21 CPU 928B Central Processing Unit

Product Overview

The Siemens 6ES5928-3UB21 (6ES59283UB21) is a high-performance CPU 928B central processing unit designed for the SIMATIC S5-135U and S5-155U multi-processor controller systems. This "New Version" single-width module represents one of the most powerful processing options for the S5 family, engineered to handle extremely complex logic and high-speed data processing tasks. A standout feature of the CPU 928B is its integrated SS slot, which allows for the installation of a second serial interface, enabling simultaneous communication with multiple HMI, SCADA, or peer-to-peer networks. In mission-critical environments like automotive powertrain assembly and continuous chemical processing, the 6ES5928-3UB21 provides the deterministic execution and high-speed floating-point arithmetic necessary to maintain peak operational throughput.

Technical Configuration

The CPU 928B is built on a sophisticated hardware platform that enables it to operate as either a standalone controller or as part of a multi-processor rack.

• Dual Interface Capability: The dedicated SS (Sub-Slot) interface allows for modular expansion, supporting various communication protocols for localized or remote data exchange.

• Instruction Processing: Optimized for rapid execution of STEP 5 code, specifically handling complex mathematical functions and large data block (DB) structures with minimal scan time impact.

• Single-Width Form Factor: Despite its advanced processing capabilities, the module occupies only one slot in the S5 rack, allowing for higher I/O density and module variety in the main chassis.

• Diagnostic Monitoring: The front panel features a comprehensive array of LED indicators for hardware health, cycle time monitoring, and bus status, facilitating rapid on-site troubleshooting.

• Memory Submodule Port: Features a high-retention slot for external EPROM or RAM submodules, ensuring secure program storage and easy version control.

Technical Specifications

Technical FAQs

What is the advantage of the CPU 928B over the standard CPU 928?

The "B" version (6ES5928-3UB21) includes the additional interface slot (SS slot), providing significantly more flexibility for networking and data logging without requiring a separate communication processor (CP) module.

How do I address the second interface in my STEP 5 program?

The second interface is addressed via specific system function blocks (SFBs) or through the configuration of the interface submodule installed in the SS slot. Ensure your COM software version supports the specific submodule used.

Is this module RoHS compliant?

Based on its industrial legacy status, this product is not RoHS-compliant. It contains lead and diboron trioxide above 0.1% thresholds, which is standard for high-durability electronic components of this era.

Engineering & Installation Guide

• Submodule Security: When installing a second interface into the SS slot or a memory submodule into the main port, ensure the PLC power is off. Use the mechanical locking levers to ensure the submodules are fully seated; a loose connection here can cause intermittent "QVZ" (Timeout) errors or CPU resets during machine vibration.

• Multi-Processor Synchronization: If using the CPU 928B in a rack with other CPUs (such as a CPU 922), you must correctly configure the "Interrupt Stack" and coordination bits in the DB1. This ensures that the processors do not collide when accessing the same I/O images or global data blocks.

• Thermal Management: Despite its single-width design, the 928B generates significant heat due to its high clock speed. Ensure the S5 rack fan tray is fully operational. If the CPU temperature exceeds internal thresholds, it may trigger a "Stop" condition to protect the CMOS logic.