A data read start decision device includes: a storing circuit configured to store code key data; a read check circuit configured to output a read start signal in response to code key data read from the storing circuit, and a controller configured to start reading environment setting data from the storing circuit in response to the read start signal. The read check circuit is configured to at least one of: receive the read start signal from the controller and transfer the read start signal to the controller in response to the read code key data; and generate the read start signal based on the read code key data and output the read start signal to the controller.