A method and apparatus for implementing power modes in microcontrollers (MCUs) using power profiles. In one embodiment of the method, a central processing unit (CPU) of the MCU executes a first instruction for calling a subroutine stored in a memory of the MCU, wherein the first instruction comprises a first parameter to be passed to the subroutine. Thereafter the CPU writes a first value to a first special function register (SFR) of the MCU in response to executing the first instruction, wherein the first value is related to the first parameter. The MCU operates in a first power mode in response to the CPU writing the first value to the first SFR. The CPU also executes a second instruction for calling the subroutine, wherein the second instruction comprises a second parameter to be passed to the subroutine. In response the CPU writes a second value to a second SFR of the MCU in response to executing the second instruction, wherein the second value is related to the second parameter. The MCU operates in a second power mode in response to the CPU writing the second value to the second SFR. The MCU consumes more power operating in the first power mode than it does when operating in the second power mode.