s7 200 question

dear plc friends
i am in process of learning plc programming.can any one help me to make a small program to operate one out of two pumps alternately.With first start up pump1 should come on and pump2 off.during next start pump2 on and pump1 off.inputs available are ON and OFF push buttons.I hope someone out there will respond.type of plc is siemens s7 300 or s7 200

vinuvinod,

There are many way to do this. It is often called a "flip-flop", or an "alternator". Here is how to do it in two rungs using Siemens S7 (I0.0 = PUMPS ON PUSHBUTTON, I0.1 = PUMPS OFF PUSHBUTTON, MO.0 = PUMP 1 RUN, MO.1 = PUMP 2 RUN, Q0.0/1 = FLIP_FLOP

NETWORK 1:
LDN I0.1
LD I0.0
O M0.0
ALD
AN M0.1
= M0.0
S Q0.0, 1

NETWORK 2:
LDN I0.1
LD I0.0
A Q0.0
O M0.1
ALD
AN M0.0
= M0.1
R Q0.0, 1

I must be having a bad case of Deja-Vue. I could sweare I saw this question and answer HERE!