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- Product Core Brief
- Model: ABB PM856A 3BSE066490R1
- Brand: ABB
- Series: AC 800M High Performance
- Core Function: Main CPU for process control
- Product Type: Processor module
- Key Specs: 16 MB RAM; 24 MHz clock; 0.46 ms/1000 bool ops
- Condition: New Original / New Surplus
- PM856A 3BSE066490R1
- Key Technical Specifications
| Parameter | Value |
|---|---|
| Clock frequency | 24 MHz |
| Performance (1000 bool ops) | 0.46 ms |
| RAM total | 16 MB |
| RAM for application | 10.337 MB (800xA 5.1 FP4+) |
| Flash memory | Yes, for firmware storage |
| Redundancy support | No (non-redundant model) |
| High Integrity | No |
| Ethernet ports | 2 x RJ45 (CN1, CN2) |
| Serial ports | 2 x RJ45 (COM3 RS-232C, COM4 isolated) |
| Power supply | 24 V DC (19.2-30 V) via baseplate |
| Power consumption | 8-12 W typical |
| Operating temperature | 0 to +55 °C |
| Dimensions (W x H x D) | 119 x 186 x 135 mm |
| Weight | 1.2 kg |
| Mounting | DIN-rail via baseplate |
- Product Introduction
The ABB PM856A 3BSE066490R1 is a processor module in the AC 800M High Performance series, running control applications in System 800xA DCS setups. It handles logic execution, I/O scanning, and communication via dual Ethernet and serial ports on the baseplate.
Teams install it in non-redundant controllers for mid-sized processes like batch or continuous lines, where 16 MB RAM and 0.46 ms scan times cover most needs without jumping to pricier PM86x variants. Matches fieldbus modules directly for Profibus or Ethernet/IP integration.800xahardwareselector.automation.
- Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| No power LED or boot | Baseplate power fault or slot contact | ✅ Medium | Measure 24 V DC at baseplate pins; reseat module | Fix supply first; cycle INIT button if voltage good but no boot. |
| Application hangs on load | CompactFlash corrupt or RAM test fail | ✅ High | Run diagnostics via DTMTool; test with blank CF card | Reflash CF; replace PM856A if RAM self-test fails repeatedly. |
| Ethernet link down both ports | Cable, switch, or IP config mismatch | ✅ Medium | Ping module IP from engineering station; check LEDs | Verify Control Builder config; swap cable/port before swapping CPU. |
| Watchdog trips randomly | Task overload or power ripple | ✅ High | Monitor CPU load in diagnostics; scope 24 V supply | Tune tasks or stabilize power; reload app if load spikes on specific code. |
| Serial COM3/4 no response | Baud/parity wrong or cable fault | ✅ Low | Loopback test on port; check DTMTool comms settings | Confirm config matches tool; test with known-good cable before module swap. |
| High scan time warnings | Too many tasks or I/O points | ❌ Low | Check task scan times in Control Builder Online | Optimize code; add I/O processors if PM856A pegged at limit. |
| Module hot or fanless overheat | Ambient >55 °C or baseplate cooling fail | ✅ Low | Measure case temp; verify rack airflow | Improve ventilation; derate if cabinet exceeds spec. |
| Firmware mismatch on startup | CF card has wrong 800xA version | ✅ High | Note error code; verify CF against latest compatible firmware | Update CF with matching 800xA release; full cold start after. |
Power down, photo the LEDs/baseplate wiring/error screen, then hit support with logs from Control Builder—cuts debug time in half.
- Frequently Asked Questions (FAQ)
Q1: What baseplate does the ABB PM856A 3BSE066490R1 need?
It mounts on the standard AC 800M High Performance baseplate with power, Ethernet (CN1/CN2), and serial (COM3/COM4) ports. Snap a photo of your existing setup to confirm connector layout before ordering.
Q2: Direct swap for older PM85x CPUs?
Yes for same series, but backup your application first—PM856A expects 800xA 5.1+ compatible code. Cold start after insert, reload via CompactFlash or DTMTool, then online test I/O binding. Takes 20-30 minutes typically.
Q3: Does it run redundant?
No, PM856A is simplex only. Go PM861/864/866 if you need <10 ms switchover redundancy. Fine for standalone controllers where single-point failure is acceptable.
Q4: Hot-swappable in live rack?
Do not. Pull 24 V from baseplate, wait 30 seconds for discharge, swap, then repower. Live insert risks backplane glitch or corrupted app load—seen it lock entire controllers before.
Q5: Current production or surplus-only?
Active in ABB’s AC 800M lineup, but exact 3BSE066490R1 shows in surplus channels from upgrades. Performs identical to factory; just verify firmware compatibility with your 800xA version.
Q6: New Surplus vs. factory fresh pricing?
Surplus means unused from spares/overbuys—same spec, no factory markup or lead time. Expect bench power-up and diagnostic run from reputable sellers to confirm CF slot and RAM pass.
Q7: Warranty and test docs on surplus PM856A?
12 months standard, after full test: power-on, self-test pass, Ethernet link-up, and basic app load on AC 800M sim rack. Ask for the report with serial number matched to photos—proves it’s ready.
