The Fanuc OT 900 parameter list is not just a set of numbers; it is the definitive blueprint of your lathe’s capabilities. Understanding this list allows you to:
✅ Diagnose why certain G-codes don't work
✅ Restore purchased options lost during battery failure
✅ Unlock productivity features (rigid tapping, DNC, macro B)
✅ Avoid costly service calls for 5-minute parameter changes
Before editing, always capture the "original state" of parameters 900–909. Write them down in your machine logbook. And remember: On a 40-year-old control, the difference between a basic turning center and a full C-axis live-tooling machine is often just one bit in the 900 list.
If you are unsure about your specific Fanuc OT version, consult your machine tool builder’s original parameter sheet or a certified Fanuc technician. Use this guide as a roadmap, not as an absolute authority for every permutation of the OT control.
Looking for a specific 900 parameter function not listed? Leave your machine model and Fanuc ROM version in the comments below (or consult your local service manual for ROM-specific bit mapping).
The Fanuc 0-T (often written as Fanuc OT) is a legendary workhorse in the world of CNC turning. While standard parameters handle day-to-day operations like feed rates and motor tuning, the 900-series parameters are the "keys to the kingdom"—they unlock machine options that were originally sold as premium add-ons by the manufacturer. The "Secret" Nature of 900 Parameters fanuc ot 900 parameter list
In the Fanuc universe, 900-series parameters are unique because they are bit-based. Instead of a single number, each parameter is a string of eight 0s and 1s. Flipping a single bit from 0 to 1 can suddenly give your machine a feature it didn't have yesterday, such as:
Canned Cycles: Automating complex drilling or threading with a single line of code.
Custom Macros: Enabling "Custom Macro A" for advanced programming logic.
Memory Upgrades: Artificially expanding the storage for your NC programs. Essential Fanuc 0-T 900 Parameter Map
Based on technical documentation, here is a snapshot of what these bits actually control: Description Functionality Unlocked 900 CANNED CYCLE Enables standard G-code cycles like G81/G83. 900 G10 PROGRAM INPUT Allows software to update offsets automatically. 900 INCH / METRIC Toggle between imperial and metric measurement systems. 901 TAPE MEMORY Controls memory capacity (from 20M to 320M). 901 CHAMFER/RADIUS Enables corner rounding/chamfering G-codes. 902 CONSTANT SURFACE Allows the spindle to adjust speed based on diameter. 902 CUSTOM MACRO A Unlocks the ability to use variables and logic. 903 Enables the dynamic buttons below the CRT screen. 904 Changes the system text (Japanese, German, Spanish, etc.). How to "Unlock" These Settings The Fanuc OT 900 parameter list is not
Because these parameters affect the machine’s core configuration, they are protected by a safety lock called PWE (Parameter Write Enable).
Enter MDI Mode: You cannot change parameters while the machine is running or in Jog mode.
Toggle PWE: Go to the SETTING page and find PARAMETER WRITE. Change the 0 to a 1. The machine will trigger a "P/S 100" alarm—this is normal and just means the system is in "unlocked" mode.
Navigate to 900s: Press the SYSTEM key and search for the specific parameter (e.g., 901).
The Edit: Type the entire 8-bit string (e.g., 00100000) and press INPUT. Looking for a specific 900 parameter function not listed
Restart: Many 900-series changes require a "Cold Start" (powering the machine off and back on) to take effect. A Word of Caution
The 900 parameters are essentially the "firmware" settings of your lathe. While it's tempting to "turn everything on," incorrect settings can cause system crashes or render the machine unresponsive. Always back up your existing parameters before making changes, as many older 0-T controls do not have a "factory reset" button that restores these specific bits. Fanuc Ot 900 Parameter List - Google Groups
| Bit | Name | Function | | :--- | :--- | :--- | | 0 | MA2 | Macro B (G65 with expressions, DO/WHILE loops) – Highly valuable | | 1 | GRA | Graphic display (tool path simulation on CRT) | | 2 | SPM | Spindle error detection (load meter, speed arrival check) | | 3 | PMV | Program mirror image (for dual turrets) | | 4 | PLF | Polygon turning (G77, G78) | | 5 | PS1 | Punch special codes 1 | | 6 | PS2 | Punch special codes 2 | | 7 | SHP | Shop floor programming (conversational) |
| Bit | Function |
|------|-----------|
| 7-6 | PMC model: 00 = PMC-L, 01 = PMC-M, 10 = PMC-R (most OT) |
| 5 | Number of PMC I/O slots |
| 4 | I/O link mode (0 = normal, 1 = high speed) |
| 3-0 | Diagnostic memory size: 0010 = 4K, 0100 = 8K, 1000=16K |
The 900 series is interesting because it reveals that Fanuc hardware is often the same, but the software locks differ.
You might buy a used lathe that "doesn't have rigid tapping." However, if you look at the 900-series parameters, you might find the bit for rigid tapping is simply set to 0. In the 90s, machine builders would physically sell the same machine with different features enabled/disabled via these bits.