repetitive cycle on Fanuc 21 TA

Recently I want to add repetitive cycle function on my Fanuc 21TA. I changed the option parameter but the bit stayyed '0'. Could anybody tell me why? or is there any special procedure to do this..?
I need your help guys..:confused:

Fanuc controls have a PWE bit (parameter write enable) which must be set to '1' before other parameters can be changed.

Not sure what location the Fanuc 21 TA uses, but it should be listed in your user manual.

Make sure that the bit is reset to '0' after the changes have been made.

PWE screen should be obtained by pressing the offset/settings key on the controller (it may take a couple of time when pressing the offset/settings key) to change this to write enable you must have your mode select switch to MDI from there you can change the parameter you want while you are still in MDI mode when you are done changing the parameter you needed to change don't forget to change the write enable back to write disable still being in the MDI mode selection , hope this helps!

Turn the edit key to enable.

Hmm,, arent there passwords used on 16,18,21 ?

Thanks guys for your replies.. but I had tried to set it with PWE on, MDI mode on and edit key enabled. May be M-man's right, arent there passwords used on 16,18,21 ?

Which alarm appers when you try the change the parameter?

Mabe it will work if you punch all parameters to Pc and change them there and then load them back to machine...

Which parameter are you trying to change?

I changed prmtr 9921#7, then alarm 'POWER MUST BE OFF' appeared. Then I tried to punch the nc parameter to PC, change 9921#7 to 1, and upload back to machine. the bit stayed 0.. and again alarm 'POWER MUST BE OFF' appeared.. any ideas?

Some parameters changes do not take effect until the control is powered down then powered up again.

Are you sure that the parameter is unchanged when you power up?

The parameter remained unchanged when i powered up..