Control device for automatic transmission

A method of operating an automatic transmission capable of operating in an automatic shift mode in which a gear ratio is automatically selected based on driving conditions of a vehicle, and also capable of operating in a manual shift mode in which the gear ratio is changed based on an upshift command or a downshift command by manual operation of a manual operation device, the method comprising:

• determining whether the downshift command has been operated by the manual operation device in the manual shift mode;
• changing and setting the gear ratio after downshift depending on a degree of requirement for deceleration based on a driving operation when the downshift command has been operated by the manual operation device in the manual shift mode;
• and
• performing the downshift to the gear ratio that has been changed and set,
• wherein the changing and setting of the gear ratio after the downshift depends on an elapsed time from an accelerator release operation to a downshift command operation and a vehicle speed that serve as the degree of requirement for deceleration.