If it's necessary for creature to have a delay in decisions due to calculations (involving memory, stimuli, etc) then it needs consciousness. If decisions must be understood by you through reason + awareness, then you have reasonable consciousness. Animals and most humans have unreasonable consciousness, where understanding comes through feelings and emotions, and thoughts just another stimuli. Free will exist only in decisions that you can make by choosing fallow instinctive illusory nature or Reasonable nature through awareness. Reasonable nature in my view is atman in vedanta conception. Everything in the Universe driven by specific script/code/software/whatever you call it. There is layered determinism, where the lower level program can be override by the higher layer. For example, if your body and brain still ran by instinctive guidance, but you are trying to be awakened and ignore that lower level code, you choose higher level of guidance and your atman (holy reason) suppress instincts as nothing fight at all. But if you fight instincts on your own, you will fail.