S7 300 RAM to ROM on an S120

Hi, I have a problem with this function.

I'm using SFB53 to write a '1' to P977 and it "appears to work".

I can see P977 change in Starter when the function is activated from the PLC. If I change any settable parameters (i.e. P210, P1080 etc), these are saved in ROM, but it appears that after calibrating the encoder, the absolute encoder offset is NOT saved.

As a test, when I use Starter to activate P977, the encoder offset is saved as expected.

What is going on?

See attached.

Regards,

Graeme

Hi TechTeam,

I was triggering P977 in the expert list to match what the PLC was doing - so it works when I change P977 in the expert list, but when I see the PLC changes P977 it does not work.

We also tried triggering P971 on the Drive object, but this did not retain the Abs encoder offset.

Confused! 

Regards,

Graeme

Hi Graeme,

do you have an absolute multiturn or singleturn encoder? In case of singleturn encoder: did you activate the position tracking? Was the drive turned further after adjusting the encoder and before or even after switching off the device?

Hi all, it was us being daft.

Instead of directly writing P2507=2 (and monitor for the change P2507=3) AND THEN setting P971=1 on the DO, which works fine, We were writing to the Homing block input signal "Set reference point" which really misleadingly changes the position actual value to whatever the home coordinate value you set in P2599 - but this DOES NOT save the calculated offset when you trigger P971=1 on the DO.

Had this POST been somewhat better described in the subject, I would have found the correct sequence earlier - I was searching for strings like "absolute" "encoder" "offset" "RAM" "ROM" etc

Regards,

Graeme