Description
The ABB PM851AK01 (3BSE066485R1) is a central processing unit sub-bundle designed for the AC 800M hardware platform within the Ability System 800xA and Compact Product Suite architectures. Operating as a cost-efficient entry-level controller for standalone utility sub-systems or small-scale plant applications, this assembly executes control logic and handles system communication over integrated interfaces. The sub-bundle natively includes the PM851A CPU module alongside its matching TP830 baseplate and termination kit.
Commercial Availability & Lifecycle Status
- Condition: Factory Sealed, New Surplus (Original OEM packaging with intact factory seals)
- Warranty: 12-Month Comprehensive Technical Warranty
- Availability: In Stock (Global priority air freight shipping within 24–48 hours)
- Pricing Note: Price is subject to component market conditions and regional stock levels. Contact our industrial sales engineering desk for a firm, written quote.
Technical Specifications
| Parameter | Value / Specification |
| ABB Part Number | 3BSE066485R1 |
| ABB Type Designation | PM851AK01 (Sub-bundle including PM851A CPU and TP830 Baseplate) |
| Processor Type | 32-bit RISC Motorola MPC860 |
| Clock Frequency | 24 MHz |
| On-Board RAM | 12 MB (6.253 MB available for application runtime) |
| Flash Memory | 2 MB (For firmware storage) |
| Power Input | 24 V DC (Accepts 19.2 to 30 V DC range) |
| Power Dissipation | 4.32 W nominal (7.2 W maximum) |
| Operating Temperature | 0 to +55°C (+32 to +131°F) |
| Storage Temperature | −40 to +70°C (−40 to +158°F) |
| Protection Class | IP20 according to EN 60529 |
| Hazardous Location Certs | cULus Class 1, Zone 2, AEx nA IIC T4 Gc X |
Architecture & Communication Interfaces
The PM851AK01 runs tasks configured through the 800xA Control Builder software using standard IEC 61131-3 languages. It is built strictly for non-redundant installations. Within a hierarchical control network, the processor communicates with supervisory levels via the MMS (Manufacturing Message Specification) protocol over an Ethernet backbone.
Data Link Capabilities
- Ethernet Ports: 1 × 10 Mbit/s RJ-45 interface (IEEE 802.3) dedicated to the Control Network.
- Serial Channels: 2 × RS-232C ports (COM3 is non-isolated with full RTS/CTS handshaking; COM4 is opto-isolated and typically reserved for service/diagnostic tool attachment).
- CEX-Bus Expansion: Supports the addition of 1 communication interface module (such as a Profibus DP V1 master) via the local CEX-bus interface.
- ModuleBus Interface: Supports direct connection to local S800 I/O clusters, handling up to 24 I/O modules max across 1 electrical and 1 optical cluster.
Migration, Engineering Constraints & Component Package
The PM851AK01 serves as the modern hardware functional replacement for the legacy PM851K01 processor variant. When scheduling a retrofit or hot-swapping older processor modules with this variant, engineers must verify specific mechanical and environmental constraints:
- Firmware and Memory Baseline: Because this module features a 12 MB RAM footprint, ensure your System 800xA software version matches or exceeds 5.1 FP4 to correctly allocate application code boundaries without throwing compiler memory faults.
- Redundancy Limitations: The PM851A architecture does not possess the secondary hardware synchronization registers required for hot-standby configurations. If your loop criticality demands dual-CPU tracking, you must select the PM864A or PM866 series controllers.
- Included Package Components: The 3BSE066485R1 part number corresponds to a full kit, which includes:
- PM851A CPU Module
- TP830 Baseplate (115 mm width)
- TB850 CEX-bus Terminator
- TB807 ModuleBus Terminator
- 3.6 V Lithium Backup Battery (Part No: 4943013-6)
- Note: Base software licenses are not packaged with the hardware block and must be ordered separately.
Field Engineering Note: The 3.6 V lithium backup battery maintains the RAM application space for up to 72 hours during a full auxiliary power interruption. When swapping out a depleted battery module, perform the changeout while the 24 V DC auxiliary input remains completely energized. Removing the battery while the rack power is disabled will result in an immediate loss of the volatile application program.
Frequently Asked Questions
Can I run a Profibus master and a Modbus RTU link simultaneously on this CPU?
Yes. You can configure one of the on-board RS-232C serial ports (COM3) as a Modbus RTU Master or Slave link using standard Control Builder libraries, while simultaneously mounting a CI854A Profibus module on the CEX-bus to poll remote I/O drops.
What causes an “OVR” or task overrun LED status indication on this specific unit?
The PM851A utilizes a 24 MHz clock speed. If you load the application with complex mathematical logic or set the execution cycle time too tight (e.g., down to 1–5 ms intervals on heavy floating-point blocks), the CPU will run out of calculation time margins within the scheduled task window, tripping an overrun fault. Keep fast task execution blocks reserved for critical logic only.
Is the PM851AK01 baseplate compatible with older PM851 CPU revisions?
The included TP830 baseplate is standard across the non-redundant AC 800M series. However, the physical module placement tolerances require clean backplane pin paths. Verify with the OEM datasheet that your target CPU firmware generation matches the backplane revision before running an active installation insert.
