Product Core Brief

• Model:
• Brand: GE Fanuc / Emerson
• Series: PACSystems RX3i
• Core Function: Ethernet Network Interface Unit (ENIU / NIU). Acts as standalone remote I/O station controller, scans local backplane I/O and exchanges cyclic I/O data with host PLC via EGD (Ethernet Global Data).
• Product Type: Remote I/O NIU Station Controller
• Key Specs: Dual backplane bus (RX3i PCI + Series 90-30 serial expansion bus) | RS232 + RS485 onboard serial ports | Requires paired IC695ETM001 Ethernet module | Supports limited local logic (20KB) Note: Legacy RX3i hardware; new original stock limited, surplus & refurbished widely available. IMPORTANT: NIU itself has NO built-in Ethernet port; must install IC695ETM001 in adjacent slot. Hot swap of the NIU module itself is NOT supported.

 

Key Technical Specifications

• Processor Architecture: Dedicated NIU controller, supports floating-point math
• Local User Logic Memory: Max 20KB (LD/FBD/ST; excludes C blocks)
• Onboard Flash Storage: 10 MB for data logging / parameter storage
• Serial Interfaces
  • COM1: RS-232
  • COM2: RS-485
• Serial Protocols: SNP, Serial I/O, Modbus RTU Master/Slave
• Backplane Bus Support: Dual bus
  • Native RX3i PCI backplane
  • Series 90-30 serial expansion bus (compatible with IC693 series I/O modules)
• Power Consumption +3.3 VDC: 1.25 A +5 VDC: 1.0 A
• Battery-backed RTC: Requires IC695ACC302 / IC698ACC701 lithium battery for memory retention
• Status LEDs: NIU OK, SCANNING I/O, OUTPUTS ENABLED, I/O FORCE, SYS FLT, COM1 / COM2 activity
• Maximum I/O Capacity per station Discrete: 2048 Input / 2048 Output Analog: 1264 %AI / 512 %AQ
• Expansion Capability: Supports up to 7 expansion racks via IC695LRE001 serial expansion transceiver
• Ethernet Communication: Dependent on IC695ETM001; uses EGD for cyclic remote I/O exchange
• Operating Temperature: 0°C ~ +60°C horizontal cabinet mounting
• Storage Temperature: -40°C ~ +85°C
• Form Factor: Single-width RX3i module
• Compatible Baseplates: IC695CHS012, IC695CHS016 universal RX3i racks
• Supported Software: Proficy Machine Edition v5.51 or newer
• Agency Approvals: UL508, Class I Div.2, CE

 

Product Introduction

is an Ethernet Remote I/O Station Controller (ENIU) for PACSystems RX3i platform. It builds a fully independent remote I/O station without needing a local RX3i CPU. The NIU continuously scans all RX3i I/O modules and optional Series 90-30 I/O on expansion racks, then exchanges all %I/%Q/%AI/%AQ data with a main master PLC over Ethernet using EGD protocol.

A unique feature: it can run small segments of local logic (20KB) inside the remote station, enabling basic autonomous control if Ethernet communication to the master is lost. Commonly used for large distributed plant retrofits, mixed RX3i + Series 90-30 hybrid I/O systems, and long-distance remote machine panels connected over factory Ethernet.

Critical Layout Rule: + IC695ETM001 must be installed adjacent to each other; backplane communication between NIU and ETM is mandatory.

 

QA & Testing SOP (Transparency Building)

1. Incoming Inspection: Verify part marking and hardware revision. Inspect backplane edge pins for bending/corrosion; inspect D-Sub serial connectors and housing damage.
2. Live Testing: Mount onto validated RX3i baseplate with IC695ETM001. Establish EGD communication with RX3i master CPU, load I/O configuration, execute continuous 24-hour cyclic I/O scanning test.
3. Electrical Testing: Monitor backplane 3.3V/5V rail stability. Insulation resistance ≥10MΩ between serial field terminals and chassis ground.
4. Firmware & Documentation: Record firmware revision, photograph front panel switch settings and serial port layout before erasing resident configuration.
5. Final QC & Packaging: Place unit inside anti-static bag; attach dated QC test tag confirming I/O scanning, serial port and Ethernet EGD communication validation prior to shipment.

 

Installation Pitfalls & Guide (Engineer to Engineer)

❗ No Hot Swap for NIU Module: You cannot hot-swap . Full rack power shutdown required before removal. Standard I/O modules support hot swap on hot-swap rated baseplates, but the NIU controller does not. ❗ Ethernet Module Dependency: NIU has no RJ45 port. Missing or misplaced IC695ETM001 results in zero Ethernet communication. ❗ Adjacent Slot Requirement: NIU and ETM001 must occupy neighboring slots; separated slots break internal backplane messaging between NIU and Ethernet module. ❗ Mixed I/O Caution: Series 90-30 I/O can only be deployed on serial expansion racks (IC695LRE001). You cannot plug IC693 modules directly into RX3i main baseplate. ❗ Local Logic Memory Limit: Max 20KB logic; C-program blocks are NOT supported on NIU. Complex control requires full RX3i CPU instead. ❗ Battery Maintenance: Without lithium battery, real-time clock and retentive data are lost after power cycle. ❗ ESD Risk: Static discharge can damage serial transceivers and backplane interface; causes intermittent serial communication faults.

Replacement Guide:

1. Pre-install: Lockout-tagout rack power; back up master PLC EGD configuration. Photograph slot layout, serial wiring and Ethernet cable connections.
2. Removal: Disconnect serial cables, remove adjacent first, extract NIU module without twisting backplane pins.
3. Install: Insert new into original slot, re-seat into adjacent slot; reconnect serial and Ethernet wiring.
4. Power-on Test: Restore rack power, confirm NIU OK LED steady; download matching configuration, verify master PLC receives all remote I/O data and check for EGD exchange faults.

 

FAQ (Frequently Asked Questions)

Q: Does support hot swapping? A: No. The NIU controller module itself cannot be hot swapped. Local I/O modules support hot swap on certified RX3i baseplates.

Q: What is the difference between and ? A:

• = Remote I/O station controller (scans I/O, manages station logic, serial ports)
• = Ethernet interface only (no I/O scanning capability). Must pair with NIU to enable remote I/O networking.

Q: Can work without an RX3i CPU on the remote rack? A: Yes. This is its core purpose — it operates as a standalone remote I/O slave station without local CPU.

Q: Can this module communicate using Modbus TCP natively? A: No. Primary remote I/O transport is EGD. Modbus TCP requires separate Ethernet module logic or gateway configuration on the master side.

Q: Can I mix Series 90-30 and RX3i I/O on the same NIU station? A: Yes. RX3i I/O on main baseplate; IC693 Series 90-30 I/O via IC695LRE001 serial expansion racks.

Q: Will the configuration automatically load onto a replacement NIU? A: I/O layout and EGD exchange definitions reside in the master PLC. After replacement, verify network IP settings on and perform full I/O point validation.

Q: Can multiple EGD masters communicate to one NIU station? A: Yes, EGD supports multiple peer devices reading/writing remote I/O data, but network load and update timing must be carefully engineered.

Q: What happens if Ethernet cable fails between master and NIU? A: The NIU can execute preloaded local logic (if programmed) and hold outputs according to configured fail-safe behavior until communication recovers.