learning programming

hi
i am a learner working with siemens plc.I m trying to make a program , where i have to generate one index.When input1 gets high, the index starts from 0 and after 20 minutes it becomes 1.Same way when the input1 goes low, the index starts gettting decrease and after 30 minutes it becomes 0.
I was trying to start one timer as input1 goes high.and them i am dividing 20 with running time value so that when the running value of timer becomes 20 the output of divid block will come 1.
but it is not working.I think i am making some mistake.Please help me.

Here's one implementation:

plc program

hi ld
thanks for your reply.but my intention is , when input i 1.0 goes high.... i have to increase index from 0 to 1 with in 20 minutes.This 0 to 1 is not digital but the value will increase from 0 graduallly and reaches 1 after 20 minutes.
and reverse when i 1.0 goes low or off in 30 minutes.

...

thanks once again
i am trying this but when the input gets low the value stars going to negative and never reach at zero.....where as when the input goes high...it is working perfectly and index reaching up to 1........

??

whenever the input i1.0 becomes low,the value of MD90 becomes zero and then starts decreasing and goes on towards minus...

You have entered the code incorrectly - notice that the compare instructions are not the same.

thanks

great......
so nice of you LD ,
You are right.I wrote the wrong code.Now it is ok.....
thank you