Description

ABB PM856AK01 STU Processor Unit

The ABB PM856AK01 STU 3BSE069514R1, also cataloged as the PM856AK01 Processor Unit, provides CPU execution, communication handling, and I/O data processing functions within ABB AC 800M System 800xA controller platforms.

Hardware Specifications

Parameter	Specification
Model	PM856AK01 STU
Brand	ABB
Origin	Sweden
Product Type	AC 800M Processor Unit
Order Number	3BSE069514R1
Controller Platform	AC 800M
System Compatibility	ABB System 800xA
Processor Type	MPC860
Clock Frequency	24 MHz
Performance	0.46 ms per 1000 Boolean operations
Memory	16 MB
Application RAM Available	10.337 MB
Firmware Storage	2 MB Flash PROM
Redundancy	No
High Integrity	No
Power Supply	24 VDC (19.2 to 30 VDC)
Power Consumption	180 mA typical / 300 mA maximum at 24 VDC
Power Dissipation	4.32 W typical / 7.2 W maximum
Backup Battery	Lithium 3.6 V
Ethernet Ports	2 x RJ45
Ethernet Standard	IEEE 802.3
Ethernet Speed	10 Mbit/s
Control Network Protocol	MMS and IAC
Serial Interfaces	2 x RS-232C
COM3 Interface	RS-232C with modem control signals, 75 to 19200 baud
COM4 Interface	Isolated RS-232C service port, 9600 baud
ModuleBus Capacity	Maximum 96 I/O modules
CEX Bus Capacity	Maximum 12 single CEX bus modules
Applications per Controller	32
Programs per Application	64
Diagrams per Application	128
Tasks per Controller	32
Minimum Cycle Time	Down to 1 ms
Real-Time Clock Stability	100 ppm
Operating Temp	0 to +55 deg C
Storage Temp	-40 to +70 deg C
Relative Humidity	5 to 95 %, non-condensing
Protection Class	IP20
Dimensions	119 x 186 x 135 mm
Weight	Approximately 1.2 kg including base

Industrial Control Communication and Firmware Compatibility

The ABB PM856AK01 STU processor unit communicates with AC 800M control networks through dual Ethernet RJ45 interfaces. Additionally, the controller uses ModuleBus communication for S800 I/O expansion and supports CEX bus modules for external communication functions.

The processor includes firmware storage through Flash PROM and executes Control Builder applications within the System 800xA environment. Furthermore, the controller architecture supports deterministic backplane bus communication velocity for PLC/DCS task execution and I/O density scaling through connected S800 I/O modules.

The CPU board integrates the microprocessor, RAM memory, real-time clock, LED status indicators, INIT push button, and CompactFlash interface. Therefore, the module provides centralized execution and diagnostic functions for AC 800M controller configurations.

Frequently Asked Questions

Q: Does the ABB PM856AK01 STU support redundant processor operation?
A: No. The PM856AK01 STU is a non-redundant AC 800M processor unit. Redundant controller architectures require compatible redundant processor models.

Q: Which communication interfaces are available on the PM856AK01 STU?
A: The processor provides two RJ45 Ethernet ports for Control Network communication and two RS-232C serial interfaces for service and communication functions.

Q: How does the PM856AK01 STU connect to S800 I/O modules?
A: The processor connects to S800 I/O modules through the ModuleBus interface and supports up to 96 I/O modules according to system configuration requirements.

Field Installation Guidelines

• Install the PM856AK01 STU processor unit on the specified ABB AC 800M mounting base and DIN rail assembly.
• Verify the 24 VDC power supply wiring before energizing the controller.
• Connect Ethernet communication cables according to ABB Control Network topology requirements.
• Install ModuleBus termination components correctly when connecting S800 I/O modules.
• Maintain proper cable separation between communication wiring and high-voltage power conductors.
• Connect cable shields according to industrial grounding practices to reduce electromagnetic interference.
• Check CPU LED indicators during startup, operation, and fault diagnostics.
• Confirm that the installation environment complies with operating temperature, humidity, and IP20 enclosure requirements.

Specifications

• Brand: ABB

Advantages

• High reliability in industrial environments
• Supports continuous operation
• Compatible with major PLC/DCS systems