A vehicular rearview mirror system includes an interior rearview mirror assembly having an interior electrochromic reflective element, a housing for the interior electrochromic reflective element, and digital circuitry supplying a drive signal to the interior electrochromic reflective element. The interior electrochromic reflective element assumes an interior mirror partial reflectance level in response to the interior mirror electrochromic reflective element drive signal. The digital circuitry includes a microcontroller for controlling over a vehicle network at least one other vehicle function. One of the at least one other vehicle function includes an exterior mirror assembly that may include an exterior electrochromic reflective element that assumes an exterior mirror partial reflectance level in response to an exterior mirror electrochromic reflective element drive signal. The microcontroller may control the exterior mirror partial reflectance level of the exterior electrochromic reflective element over the vehicle network.