Open evse pwm and ev communication ac charger

I am trying to build an ac charger ,I just have a few doubts
Like when we connect our gun to ev veichle and we are in state b and then we start sending pwm through cp wire to tell ev how much current we can provide and if the v is okay with it ,it will change to state c and rop voltage to 6v
but what if ev demand more or less current like how do we get to know in the mcu like how much ev want to increase and decrese our current,basically how the current negotiation will take place in ev chargers?