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3. Key Technical Specifications
| Parameter | Value |
|---|---|
| CPU Type | Max-ON Hot-Standby Redundancy CPU |
| User Memory | Up to 10 MB battery-backed RAM; 10 MB non-volatile flash |
| Boolean Execution Speed | 0.195 ms per 1000 Boolean instructions (typical) |
| Discrete I/O | 32 Kbits (%I / %Q) |
| Analog I/O | Configurable up to 32 Kwords (%AI / %AQ) |
| Program Blocks | Up to 512 (max 128 KB each) |
| Floating Point | Yes |
| Serial Ports | 1 × RS-232 + 1 × RS-485 (isolated) |
| Supported Protocols | Modbus RTU Slave, SNP, Serial I/O |
| Power Requirements | 1.0 A @ +5 VDC; 1.25 A @ +3.3 VDC |
| Battery Options | IC695ACC302 (recommended), IC693ACC302, or IC698ACC701 |
| Backplane | Universal Backplane only (PCI bus) |
| Operating Temperature | 0 to 60 °C (32 to 140 °F) |
| Clock Accuracy | TOD: ≤2 s/day; Elapsed Time: 0.01 % max |
| Redundancy | Hot-Standby via one or two dedicated Ethernet LANs (requires Max-ON software + ETM modules) |
4. Product Introduction
The GE Fanuc / Emerson IC695CMU310 is a Max-ON Hot-Standby Redundancy CPU for the PACSystems RX3i platform. It enables two complete RX3i systems to operate in a hot-standby configuration, exchanging operating data over one or two dedicated Ethernet LANs. Transfer of control from master to backup typically takes two to three logic scans while I/O states are maintained.
The CPU provides 10 MB of battery-backed RAM and 10 MB of non-volatile flash, supports floating-point math, and includes embedded RS-232 and RS-485 serial ports. It installs only in an RX3i Universal Backplane and requires Max-ON application software plus Ethernet Interface modules (IC695ETM001) for the redundancy link. Typical applications include fuel loading, standby power generation, boiler systems, and continuous manufacturing processes where brief transfer times are acceptable.
IC695CMU310
IC695CMU310
IC695CMU310
5. Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| CPU will not power / OK LED off | Backplane power or seating issue | ❌ Low | Measure +5 V and +3.3 V on Universal Backplane; reseat module | Verify power supply and slot contact |
| No redundancy synchronization | Ethernet link or Max-ON configuration error | ✅ High | Check Ethernet cables and ETM001 status; verify Max-ON software setup | Confirm dedicated LAN(s) and matching program versions |
| Program lost after power cycle | Dead or missing battery | ✅ High | Measure battery voltage; check BATT LED | Install fresh IC695ACC302 (or compatible) battery |
| Serial ports unresponsive | Cable or protocol mismatch | ✅ Medium | Test with known-good cable and terminal program | Verify RS-232/RS-485 pinout and baud settings |
| Long transfer time or I/O glitch on switchover | Scan time or network latency | ✅ Medium | Monitor scan time and Ethernet traffic during switchover | Optimize logic; ensure dedicated, low-latency Ethernet links |
| CPU not recognized in rack | Wrong backplane or firmware mismatch | ✅ High | Confirm Universal Backplane and compatible firmware | Use only IC695CHS Universal Backplane |
If the CPU continues to fault after these checks, photograph the faceplate LEDs, note the Ethernet and serial cable configurations, and capture the diagnostic logs before contacting technical support.
6. Frequently Asked Questions (FAQ)
Q: What is Max-ON redundancy? A: Max-ON is a hot-standby CPU redundancy scheme in which two identical RX3i systems exchange data over dedicated Ethernet LANs. On failure of the master, control transfers to the backup in two to three scans while I/O states are held. It is not intended for SIL 2/3 applications.
Q: What additional hardware is required for redundancy? A: Each system needs an IC695CMU310, an RX3i Universal Backplane, a power supply, one or more IC695ETM001 Ethernet modules, and the Max-ON application software. Series 90-30 expansion racks can be used optionally.
Q: How much user memory is available? A: Up to 10 MB of battery-backed RAM and 10 MB of non-volatile flash. Discrete memory is 32 Kbits; analog memory is configurable up to 32 Kwords.
Q: Does it support floating-point math? A: Yes. Floating-point instructions are fully supported.
Q: What battery should I use? A: The recommended battery is the RX3i Lithium Smart Battery IC695ACC302. Compatible alternatives include the Series 90-30 pack IC693ACC302 or the smart coin-cell pack IC698ACC701.
Q: Can this CPU be used as a standalone (non-redundant) controller? A: Technically yes, but it is designed and licensed for Max-ON redundancy applications. For standard single-CPU use, a non-redundancy model such as IC695CPU310 or CPE series is normally preferred.
Q: Can this module be hot-swapped? A: RX3i supports controlled hot-swap under the proper conditions, but a redundancy CPU should only be replaced following Emerson’s documented procedures for Max-ON systems to avoid loss of synchronization.
Q: Why is New Surplus priced lower than original list? A: These are unused original modules from OEM or distributor surplus inventory. Each unit is visually inspected, powered on a genuine RX3i Universal Backplane, and verified for basic LED and port response before shipment. Test documentation is available on request.
