plc ladder logic

hello, i'am trying to write logic where by 2 dock doors are used, if a first dock door is open, the second cant open, till the first is closed, so that both cant be open together, but can be closed together. i was wondering how i go about writing the ladder logic for this situation, and what i need to do to make this occur? your help is grealty appreciated,
thank you, mike.

Sounds like a class assignment to me!

Your first step is to make a point list - a listing of all external devices wired to the PLC and a description of their function, voltage, I/O connection point, and program address. The second is to write an english language description of the logic step by step. The third is to try writing the ladder, and then post it here for suggestions and further help.

Most of us here have a policy of helping students, but not doing their work for them. You only learn if you figure it out for yourself.

JUST IN READ YOUR QUESTION YOU CAN FOUND ANSWER.

ONE OPEN AND THE OTHER CLOSE : -| |- -|/|-

HAVE YOU A LIMIT SWITCH TO KNOW WHICH ONE IS OPEN AND WHICH ONE IS CLOSE?

IF YES, THINK ABOUT WHAT YOU NEED TO DO AND DO IT.