ABB

Models: PM851A, PM856A, PM857, PM858, PM860A, PM862, PM863, PM864A, PM865, SM811, PM866A, PM867, SM812, PM891

All belong to ABB AC 800M / System 800xA DCS platform.

• PM‑series: Main CPU processor modules (core controller of DCS)
• SM‑series (SM811 / SM812): High‑Integrity safety supervision modules for SIL‑certified safety control, paired with specific PM‑CPUsABB.
• DIN‑rail mount, 24 VDC power supply, support S800 I/O, CEX‑bus expansion, Ethernet communication, IEC 61131‑3 programmingABB Group.
• Most models are End‑of‑Life (EOL), spare market provides refurbished / used units for legacy plant maintenance.

Core Functions

Note: PM‑CPUs are main control processors, they do not directly connect field sensors; they communicate with S800 I/O modules to read/write field signals. SM811/SM812 are safety‑monitoring coprocessors, not general‑purpose I/O modules.More products: www.plcva.com

1. Real‑time process control logic execution Run IEC 61131‑3 control programs: analog PID loop control, sequential logic, interlock, motor control, sequence control. Process data from S800 I/O modules, output control commands to field devices (valves, motors, drives)ABB Group.
2. Redundancy function (supported by selected models: PM858, PM862, PM863, PM864A, PM866A, PM867, PM891) Dual‑CPU hot‑standby configuration. When primary CPU fails, backup CPU switches over within max 10 ms, no production shutdown. Supports CEX‑bus and communication redundancy for high‑availability plantsABB Group.
3. Safety‑integrity control (PM857 / PM863 / PM865 / PM867 + SM811 / SM812) TÜV‑certified IEC 61508 SIL2/SIL3 safety system.

• SM811/SM812 is the safety supervision coprocessor, runs parallel with main CPU for cross‑checking control logic, hardware self‑diagnosis, fault detection, safety trip output for emergency shutdown (ESD) applicationsABB Group.
• Safety application can run together with normal process control on same controller unit.

4. Multi‑protocol system communication Built‑in dual‑port Ethernet; expand via CEX‑bus communication modules (CI series). Support Modbus‑TCP, Profinet, Profibus‑DP, IEC 61850, DNP3. Connect to 800xA operator HMI, DCS SCADA, third‑party PLC, ABB drives, motor protection relays, etc. Support RNRP redundant network protocolABB Group.
5. Data logging, fault recording and diagnostics Store event logs, fault records; real‑time monitoring of CPU health, I/O status, communication status. Local LED status indication; remote diagnostic via engineering tool.
6. I/O system management Communicate with distributed S800 I/O via optical Modulebus, can connect multiple I/O clusters, large‑scale field signal management.

Hardware Interfaces

• 24 VDC power input
• Dual‑port on‑board Ethernet for control network
• Serial port for engineering tool debugging
• CEX‑bus expansion slot for adding communication interface modules
• Optical Modulebus interface for S800 I/O connection
• Front‑panel status LEDs, reset button, memory card slot

Main Applications & Deployment Sites

Core Application: Central process controller for ABB System 800xA / AC 800M DCS, for continuous industrial process automation, including safety‑related ESD control.

1. Thermal & Hydro Power Plants Boiler, turbine, auxiliary system DCS control. Process control for water‑steam system, fans, pumps, generator auxiliary control. Safety‑related protection logic for power‑plant safety interlock.
2. Oil & Gas, Refineries & Petrochemical Plants Process control for reactors, distillation units, pipelines; ESD emergency shutdown safety control using SIL‑rated PM+SM high‑integrity controllers.
3. Cement, Pulp & Paper, Metallurgy Heavy‑Industry Continuous production line control: kiln, mill, paper machine, smelting process; large‑scale analog and logic control.
4. Water‑treatment plants Large‑scale water‑supply and wastewater treatment plant DCS control.
5. Offshore Oil‑Gas Platforms Offshore automation control, safety shutdown system for offshore production facilities.
6. Chemical and pharmaceutical plants Process automation and safety interlock control.

Distinction summary for reference:

• PM‑series: DCS main CPU controller (brain of DCS system)
• SM811 / SM812: Safety supervision coprocessor for SIL‑rated safety control, must be used with matching PM‑CPU

• DSAI130A: S800 analog input I/O board (field signal acquisition, not CPU)
• UFC911B101: Medium‑voltage drive main‑control board for motor VFD
• REM620: Motor protection relay for motor fault protection
• UNITROL 1020: Generator excitation AVR regulator