GX developer/Mitsubishi : code changes not taking effect until after cycling power...

[Mas01]

I made a small update to the PLC logic (GX developer).
Then I wrote the updated code to the PLC (I did Online/write to PLC). I thought that would be sufficient for my code to take effect. However, the change didn't work, which left me puzzled because it was a straightforward change. I decided to cycle the PLC power for good measure, and only then did the change take effect.
Is it normal in Mitsubishi Q series PLC's (or any type of PLC for that matter) to cycle the power for the change to go live?

 

[Ronnie Sullivan]

No, you should see it straight away.
Online monitor/write will write the update as soon as you press F4

 

[AlfredoQuintero]

Configuration changes to certain intelligent modules do require power cycle, such as in the case of Ehternet modules, as the cinfiguration is sent to the module at start up. You can also use the reset switch. But changes to the program should require no power cycle.

 

[Mas01]

Thanks for the replies.
I shall keep an eye on this - hopefully it doesn't happen again! Cheers

 

[parky]

Another reason that some code will not take effect is for example where a setting programmatically done in code i.e. the initial setting of an analogue card is done on first scan bit, if the PLC is not re-booted then the configuration change would not be sent to the card. if for example you have existing card that uses only 2 of the 4 channels where on the first scan bit the settings for those channels are sent to the buffer memories & you decide to add the other channels & do an on-line change because the first scan bit is not re-triggered the information will not be sent to the card until a re-boot.
Either SM402 (first scan bit) or a NOT buffer memory bit (UG\xx) is often used to send configuration information to intelligent cards, however, in later systems most of this can be done in some configuration utility rather than the code itself.

 

[Mas01]

Thanks parky - good to know.
The code uses SM402 and SM400 (which the original programmer had aliased as 'always on') in several places.

 

[parky]

Yes SM402 is the first scan bit so it only comes on for one scan when first booted up or from stop to run.