Nexto XF – #42 - Difference between Reset Warm, Reset Cold, and Reset Origin

The objective of this tutorial is to explain the difference between Hot Reset, Cold Reset, and Source Reset in a MasterTool X project.

Components

Equipment: 1 computer/notebook.

Software: MasterTool X

Tutorial Sections

1. ARCHITECTURE
2. DEVELOPMENT

1. ARCHITECTURE

A computer/notebook will be required to use MasterTool X.

Figure 1. Computer running MasterTool X

2. DEVELOPMENT

During the development, testing, or maintenance of an application, it may be necessary to reset the PLC. In MasterTool IEC XE, this can be done through the Online menu at the top, where three types of reset are available: Hot Reset, Cold Reset, and Source Reset.

Each of them has different effects on the program and on the variables.

Reset Warm

A warm reset restarts only the program execution, maintaining as much of the controller's current state as possible.

Features:

• The code remains loaded in the PLC.
• The CPU restarts program execution.
• Normal variables are reset.
• RETAIN and PERSISTENT variables retain their values.
• Does not erase important internal data.

When to use:

• During logic tests.
• When you want to restart execution without losing important states.
• Situations where the PLC needs to return to operation quickly.

Figure 2. Warm Reset

Reset Cold

A cold reset performs a deeper reset of the controller, similar to turning the equipment off and on.

Features:

• The code remains loaded in the PLC.
• All normal variables are reset.
• RETAIN variables are reset.
• PERSISTENT variables retain their values.
• The CPU normally returns to STOP mode after the reset. 

When to use:

• To simulate a power outage.
• To validate the behavior of retentive variables.
• When you want to restart the system without erasing critical data.

Figure 3. Cold Reset

Reset Origin (Factory Reset)

The factory reset is the most drastic and returns the PLC to its initial factory conditions.

Characteristics:

• The program is removed from the PLC.
• All variables are erased, including:
  • Normal variables
  • RETAIN variables
  • PERSISTENT variables
• Internal settings can be restored to default.
• The PLC is left without any loaded application.

When to use:

• Before loading a completely new project.
• During corrective maintenance.
• When there is serious data inconsistency or unexpected behavior.
• To deliver a "clean" PLC to another project.

Figure 4. Source Reset

Summary Comparison

Important Note

• The source reset should be used with caution, as there is no code recovery after execution.

• For memory behavior testing, a cold reset is the most suitable.

• For simple logic restart, a hot reset is sufficient and safer.

This understanding is fundamental to avoid loss of important data and to correctly choose the reset type according to the project stage.