ABB PM856AK01 | 3BSE066490R1 AC 800M Processor | Legacy Controller Replacement

Description

ABB PM856AK01 | AC 800M CPU Controller

Key Technical Specifications

The processor, memory, power, application capacity and battery specifications above are taken from ABB’s AC 800M hardware selector. ABB’s controller hardware guide also gives the PM856K01/PM856AK01 package a 1.1 kg weight including the TP830 base and bus terminations.

PM856K01

Product Introduction

The ABB PM856AK01 is an AC 800M CPU module used to execute controller applications within ABB System 800xA automation architectures. Its MPC860 processor operates at 24 MHz, with 16 MB memory and application capacity dependent on the installed 800xA software release. ABB specifies support for up to 32 applications, 64 programs per application and application-program cycle times down to 1 ms.

This controller is a single, non-redundant CPU configuration. That distinction matters during replacement work because PM856AK01 should not be treated as equivalent to a redundant K02 controller simply because both belong to the AC 800M family. ABB’s current controller range separately identifies redundant configurations and different processor generations.

Application Scenarios & Field Pitfalls — The Engineer’s Perspective

Engineering Pain Point

The biggest procurement problem with this part number is the model designation itself. ABB’s current documentation consistently lists PM856AK01, while the supplied PM856K01 omits the A. Because ABB assigns a different article number to each controller configuration, the complete nameplate designation and article number should be confirmed before purchasing. Do not remove the A from the ordering code in a quotation or replacement request without checking the installed hardware.

Typical Applications

• AC 800M process controllers running control applications within System 800xA.
• PLC/DCS control applications requiring a compact single CPU architecture.
• S800 I/O control systems where the PM8xx controller provides the processing layer.
• Legacy AC 800M installations requiring maintenance replacement of an existing PM856-class CPU.

ABB describes AC 800M as a modular controller family comprising CPU modules, communication modules, power supplies and associated accessories.

Technical Pitfalls to Avoid

1. Verify the missing “A.”
   The exact ABB designation found in the current hardware selector is , article 3BSE066490R1. Treat PM856K01 as an incomplete or potentially incorrect ordering reference until the nameplate is checked.
2. Do not substitute a PM862 or PM866 solely because it is newer.
   AC 800M CPUs differ in processor speed, memory, firmware capability and system compatibility. ABB lists PM862K01 at 67 MHz/32 MB and PM866AK01 at 133 MHz/64 MB, compared with ‘s 24 MHz/16 MB.
3. Check the installed System 800xA release.
   Application memory figures can be software-version dependent. ABB specifically identifies the 10.337 MB application-memory figure for from 800xA 5.1 FP4 onward.
4. Check controller redundancy requirements.
   is listed as non-redundant. If the existing cabinet uses dual-controller redundancy, a should not be ordered as though it were a K02 package.
5. Preserve the application and firmware environment.
   Before removing the existing controller, capture the Control Builder project, controller firmware information, communication configuration, I/O topology and controller settings. A physically compatible CPU is not sufficient if the software environment is different.
6. Check the battery condition.
   ABB specifies a 3.6 V lithium backup battery. Battery status should be included in maintenance inspection, particularly on older installed controllers.

Related Products

• ABB PM851AK01 — Lower-memory AC 800M controller with 12 MB memory and 24 MHz processor architecture.
• ABB PM858K01 — 16 MB AC 800M controller with 33 MHz processing and no CPU redundancy.
• ABB PM858K02 — Redundant PM858 controller configuration; different from the single-controller PM856 configuration.
• ABB PM860AK01 — 16 MB AC 800M controller with 48 MHz processing; hardware and application compatibility must be checked.
• ABB PM862K01 — 32 MB, 67 MHz non-redundant AC 800M controller; substantially different processor and memory configuration.
• ABB PM862K02 — Redundant 32 MB AC 800M controller using the PM862 platform.
• ABB PM866AK01 — 64 MB, 133 MHz non-redundant AC 800M controller.
• ABB PM866AK02 — Redundant PM866 configuration with 64 MB memory.
• ABB TP830 — Baseplate associated with PM8xx controller packages; verify the baseplate and bus termination arrangement when replacing a complete controller package.

Procurement and Replacement Note

If the physical nameplate actually reads PM856K01, provide that exact marking to the supplier for cross-reference. The ABB documentation I verified identifies , not PM856K01, so the missing A should not be silently corrected on a purchase order.

For an installed AC 800M system, verify the complete ABB article number, CPU hardware revision, firmware, System 800xA/Control Builder version, TP830 baseplate, communication modules, S800 I/O architecture and application backup before replacement. This is particularly important for legacy AC 800M systems where the controller designation alone does not describe the complete installed configuration.