The FANUC SW alarm category is related to parameter write status. In most cases, this alarm appears when parameter writing has been enabled on the CNC. The most common code in this category is SW0100, which indicates that the Parameter Write Enable setting is turned on. This page explains what SW0100 means, when it may appear, and what users should check before changing parameters on a FANUC CNC system.
For maintenance teams, machine tool operators, and service engineers, understanding SW alarms is important because parameter write settings directly affect CNC configuration. If parameter writing is left enabled unintentionally, it can increase the risk of incorrect settings or accidental changes. At REACO CNC, we support global customers with FANUC CNC parts, repair service, and technical product supply for industrial automation systems.
These alarm references apply to:
- FANUC Series 0i-Model D
- FANUC Series 0i Mate-Model D
What Is a FANUC SW Alarm?
A FANUC SW alarm is related to the write status of CNC parameters. “SW” generally refers to the parameter write state rather than a hardware failure. In other words, this type of alarm does not usually mean that a physical component is damaged. Instead, it indicates that the control is in a condition where parameter writing is enabled or relevant parameter settings require operator attention.
What Does FANUC SW0100 Mean?
SW0100 means the parameter write switch is turned on and parameter setting is enabled. On FANUC systems, this condition is tied to the PWE setting, specifically parameter PWE (No.8900#0) = 1. This state should normally be used only when parameters need to be changed. In ordinary operation, it is recommended to keep this setting off to avoid unnecessary risk.
When Does SW0100 Usually Appear?
SW0100 commonly appears after a technician or operator enables parameter writing for setup, commissioning, maintenance, or troubleshooting. It may also be seen after parameter adjustment work if the write-enable setting is not returned to the normal state. In many shops, this is not treated as a fault alarm in the same sense as a servo or spindle alarm, but it still matters because it indicates that the control is open to parameter modification.
Why This Alarm Matters
Even though SW0100 does not usually point to a failed board, amplifier, or motor, it should not be ignored. Leaving parameter writing enabled longer than necessary can lead to unintended edits, machine behavior changes, configuration mismatch, or setup errors later in production. For that reason, service staff typically enable PWE only while performing a required parameter change and then switch it off again immediately afterward.
Basic Troubleshooting for FANUC SW0100
If SW0100 appears, first confirm whether someone intentionally enabled parameter writing. If a parameter change is currently being performed, the condition may be expected. If no parameter work is in progress, check the PWE setting and review whether it should be returned to the normal off state. It is also good practice to verify any recent parameter edits before restoring the machine to regular operation.
Typical checks include confirming whether parameter editing is required at this moment, checking whether PWE (No.8900#0) has been set to 1, reviewing recent maintenance or commissioning work, returning the parameter write setting to OFF after the required change is completed, and backing up important CNC data before making further adjustments.
Full Technical Description of FANUC SW0100
| Alarm Code | Alarm Message | Full Technical Content |
|---|---|---|
| SW0100 | Parameter write switch is ON | Parameter setting is in the enabled state. (Setting parameter PWE (No.8900#0) = 1.) Turn this parameter ON only when parameter setting is required. In all other situations, keep it OFF. |
Operator Notes for SW0100
SW0100 is often seen during service work, parameter restoration, machine setup, or control adjustment. Because the alarm indicates that writing to parameters is allowed, it should be treated carefully. Unauthorized or incorrect parameter changes may affect axis behavior, machine limits, options, communication settings, or other CNC functions. If you are not sure why PWE is enabled, it is safer to verify the machine history before making any additional edits.
Best Practice Before Changing FANUC Parameters
Before changing any FANUC parameter, it is advisable to record the original values and create a backup whenever possible. Parameter changes should be carried out only by trained personnel who understand the machine configuration and control logic. After the required modification is completed, the write-enable condition should be cleared so the CNC can return to its normal protected operating state.
About REACO CNC
REACO CNC supplies FANUC robot parts, FANUC CNC parts, Mitsubishi automation parts, and repair service for customers worldwide. If your machine shows FANUC alarms and you are also dealing with related hardware issues such as servo amplifiers, control boards, operator panels, or other CNC components, our team can help you source replacement parts and support repair needs for industrial systems.
With 34 years of industry experience, REACO CNC serves global customers who need reliable FANUC spare parts, worldwide shipping, and practical support for machine maintenance.
FAQ
Is FANUC SW0100 a hardware failure?
Not usually. SW0100 generally indicates that parameter writing is enabled, not that a physical component has failed.
What parameter is related to SW0100?
SW0100 is related to PWE, specifically parameter No.8900#0. When this value is set to 1, parameter writing is enabled.
Can I keep PWE turned on all the time?
That is not recommended. Parameter writing should normally be enabled only when a parameter change is required. In ordinary operation, it should be turned off.
Why does SW0100 appear after maintenance?
It often appears because a technician enabled parameter writing during setup or service and has not yet returned the setting to the normal state.
What should I do before changing FANUC parameters?
Back up the existing data, confirm the required values, and make sure the person performing the change understands the machine and control configuration.
Reference Source: Beijing FANUC. This article is based on technical documentation provided by Beijing FANUC.
For More Fanuc CNC repair Cases and technical articles, please back to Fanuc Technical Support Center.
Related Articles
Here are some related technical resources you may also find helpful:
- Common FANUC CNC Alarms Classification
- FANUC Common Over Travel Alarm List
- FANUC G/ M Code for a Machining Center
- FANUC G/ M Code for lathe
- How to backup SRAM file
- How to backup All data
- How to Solve FANUC alarm 5523/5524
Technical Categories
Browse our full set of technical resources:
- Common FANUC Alarms
- G & M Code Reference
- Technical Guides (Backup, Parameters, Settings)
- Repair Cases & Troubleshooting Examples
Back to Previous Page
Click here to return to the previous category page.
Back to Technical Support Home
Return to the Technical Support main page to explore all resources.
