When a FX PLC is stopped and then restarted, data register values are reset.

In some circumstances this is not desirable and here we explain how to resolve this issue.

Design Considerations

If the special bit device M8033 is set ON before the FX PLC is stopped, all the data in data registers (D registers) will retain their current value. It should be noted that some D registers are retentive by default and so the use of M8033 is not required for these registers.

Example: the PLC parameter settings below shows that for an FX2N PLC, D registers D200 – D511 are retentive by default but this setting can be adjusted by the user.

Data registers D512 – D7999 in a FX2N PLC are retentive by default and cannot be changed by the user.


For details of retentive data registers throughout the FX PLC range, please see the appropriate FX PLC programming manual.

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