Introduction: The "Secret" Parameters of the Fanuc OT Control
The Fanuc OT (also written as Fanuc 0T) is one of the most iconic and widely used CNC controls for lathes and turning centers. Despite being introduced in the mid-1980s, thousands of machines worldwide still rely on this resilient, workhorse control.
While most operators are familiar with standard parameters (0000–8999), there exists a mysterious and often misunderstood range: Parameters 900 to 999.
Colloquially known as the "900 Parameters," or the "Option Parameters," this list holds the keys to your machine’s capabilities. Unlike standard settings that control axis tuning or I/O configuration, the 900 parameters enable or disable purchased options—features like rigid tapping, macro programming, AI contour control, and additional axes. fanuc ot 900 parameter list
This article provides an exhaustive breakdown of the Fanuc OT 900 parameter list, explaining what each bit does, how to access them, and critical precautions to take before making any changes.
Your tool post won’t index. The problem is not mechanical but logical: a 900-series bit parameter tells the PMC how to interface with the turret servo or hydraulic clutch. If that bit toggles due to corruption, the turret will freeze.
Parameters 900–949 (and sometimes up to 999 depending on the ROM version) are often called "Option Parameters" or "Hardware Configuration Parameters." Unlocking the Core: The Complete Guide to the
They are stored in SRAM (Static RAM) backed by a battery. If the battery dies, these parameters are lost—and the machine becomes a brick.
The 900 series does not control feed or speed. Instead, it controls:
Critical warning: Writing a random 900 parameter set from another machine of the same model will usually not work. These values are matched to the specific hardware and PMC ladder of your exact lathe. Scenario 2: Malfunctioning Tool Turret / Indexer Your
This helps the control identify the generation of the servo system.
| Bit | Function |
|------|-----------|
| 7 | 0: X-axis not present / 1: X-axis present |
| 6 | 0: Z-axis not present / 1: Z-axis present |
| 5 | 0: No C-axis / 1: C-axis (spindle positioning) present |
| 4 | 0: No 3rd axis / 1: 3rd linear axis (e.g., Y-axis on live tooling) |
| 3-0 | Spindle type: 0000 = single speed, 0001 = two-speed, etc. |
Example: 10001000 (binary) = X axis present, Z axis present, no C, no 3rd axis, spindle type 0 (standard).
| Bit | Name | Function | | :--- | :--- | :--- | | 0 | A | ROM version A | | 1 | B | ROM version B | | 2 | C | ROM version C | | 3 | D | ROM version D | | 4-7 | - | Reserved for Fanuc factory use. Changing these WILL crash the system. |