Need timer example for s7 200

[rbduck 0]

i'm fairly new to programming Siemens PLCs. I can read the code rather well but I'm still struggling with writing. I'm learning every day. I need a simple program that initiates an output every thirty minutes. The output will be reset by an input. Regardless of when the output is reset by the input, the output must be every thirty minutes. My initial idea was to read the real time clock, making the output go hi on the hour and half hour. I'm not sure how to accomplish that. Thanks much!