F&O stocks do not have Circuit Limit’s.
There are Price Bands to ensure trading is done within the specified range to prevent erroneous order entry, as and when price approaches this levels the limits are relaxed further.
With Dynamic Price Bands, as explained above as and when price of security approaches these level the limits are relaxed further to ensure trading continues.
With Normal Price Band, as and when price hits this level trading is halted in that particular scrip.
You can read this FAQ from NSE, they have explained everything in detail there.