how to use counter on S7 300?

[arsenen8 0]

Dear Mr.PLC, Please tell me how to use count down counter to count a PV(let said 100), and i need to display the remaining time of the PV. After finish counting, the counter need to reset once a time. Hope i can have your help asap. Thanks.

[arsenen8 0]

Actually i want to build a change over function. Let say, if the countdown counter reach 0 then A is ON and B is OFF. For another counting cycle, B is ON and A is OFF. May i know there is function like TOTALIZER in the S7 program? thanks.

[arsenen8 0]

I have try to use CD counter to do it but it does not count correctly. For example, count from 20 then it will count 20,19,14,13,12,11,10........0 . Do u know wat happen? And when it is counting, i key in new PV after that when the counter reach 0 it need to reset the counter again but it will stop the plc. Please try to solve this problem for me. thanks. 2712test.zip