There isn't a Special Clock Pulse bit with a period of 2 seconds.
But there is a 1 second period clock named "Clk:1.0s.
You can use a COUNTER to generate a 2 second clock from Clk:1.0s
The trick is to make the COUTNER count up with the use of special function coil, [UpCntr].
A COUNTER with a set value of 1 will count 0,1,0,1... as an up-counter. The contact for the COUTNER will be active on the "0" count time period.
I have attached a screen shot of of the ladder logic to get this to happen.
Good luck,
Gary Dickinson