Key Technical Specifications
- Application Execution: 2x slower than PM860A (same app)
- Ethernet Ports: 2x RJ45 (CN1, CN2) at 10 Mbit/s
- Serial Ports: COM3 (RS-232C w/ modem), COM4 (isolated config)
- Supply Voltage: 24V DC (1.0A max, 2A fast fuse)
- Internal Battery Backup: Minimum 2 weeks retention
- I/O Capacity: 1x S800 I/O basic cluster (12 units)
- Fiber Module Bus: Up to 7x S800 I/O clusters
- CEX-Bus Capacity: Up to 12 communication modules
- Protection Class: IP20
- Weight: 1100g (includes PM856A, TP830, bus unit)
- Dimensions: 119mm W x 186mm H x 135mm D
- Configuration Tool: 800xA Control Builder
Product Introduction
ABB PM856AK01 3BSE066490R1 serves as a central process unit within the AC 800M controller family. It handles real-time logic execution, field equipment monitoring, and network communication for distributed control systems.Field deployment requires understanding its performance ceiling. Application execution time is exactly double that of the newer PM860A platform. The unit provides dual 10 Mbit/s Ethernet ports and internal battery backup lasting a minimum of two weeks during power loss.
Installation & Configuration Guide
Preparation (10 min)
- Verify 24V DC supply capacity includes a 20% margin for this module.
- Gather insulated screwdrivers and anti-static wrist strap.
- Locate the unique Ethernet address label on the TP830 base plate.
Removal (5–10 min)
- Disconnect power at the source.
- Release the sliding and locking mechanism on the DIN rail.
- Slide the module upward to disengage from the backplane.
- Inspect backplane connector pins for damage.
Installation (10 min)
- Align the PM856AK01 with the DIN rail and backplane.
- Slide down until the locking mechanism clicks into place.
- Connect CN1/CN2 Ethernet and COM3/COM4 serial cables.
- Verify the module is seated flush against the base plate.
Power-On & Test (10 min)
- Apply 24V DC ±10% to the power terminals.
- Observe the LED indicators for normal boot sequence.
- Establish communication via COM4 using 800xA Control Builder.
- Download configuration and verify I/O cluster recognition.
Troubleshooting Quick Reference
| Symptom | Probable Cause | Quick Check | Corrective Action |
|---|---|---|---|
| No LED activity | 24V supply failure | Measure L+ to ground | Restore 24V DC; check 2A fast fuse |
| Red fault LED | Firmware mismatch | Check revision in builder | Download matching firmware version |
| Comm loss on CN1 | Cable or port fault | Swap to CN2 port | Replace Ethernet cable; test port |
| I/O not responding | CEX-Bus overload | Count connected modules | Verify max 12 modules per CEX-Bus |
| Boot loop | Corrupt application | Connect via COM4 | Clear application; reload from backup |
Dimensions, Mounting & Wiring Notes
- Height: 186 mm
- Width: 119 mm
- Depth: 135 mm
- Mounting: DIN rail with sliding lock mechanism
- Ethernet: RJ45 (CN1, CN2) — 10Base-T, half duplex
- Serial: RJ45 (COM3, COM4) — RS-232C, up to 19200 baud
- Power Input: 3-pin terminal, 24V DC, 1.0A max
- Fiber Optic: Multi-mode or single-mode for Module Bus
FAQ
Can I swap this with a PM851AK01 without changes?
No. The PM851 only supports one Ethernet port (CN1). Redundant networking requires the PM856AK01.I lost my original configuration. Can you provide it?
We don’t store customer applications. You’ll need to rebuild from your engineering backup or OEM archives.Is this unit tested with actual I/O modules?
Yes. Every PM856AK01 undergoes a 24-hour load test with S800 I/O clusters on our dedicated test rack. Function verified under test conditions.What’s the lead time for a replacement?
Tested units ship within 1–2 business days. We keep inventory specifically for emergency downtime scenarios.Does this support CPU redundancy?
Yes. The PM856AK01 supports hot-standby CPU redundancy including CEX-Bus and communication interface failover.Do I need special tools for DIN rail removal?
Just a flat-blade screwdriver to release the sliding lock. No proprietary tools required — though your mileage may vary if the rail is corroded.Can I use third-party I/O with this controller?
Stick to ABB S800 I/O for guaranteed compatibility. Third-party modules may work but void diagnostic support.
