I have an LCD display which is powered from a pretty powerful micro, with GPU and all sorts of stuff. However, it turns out that it will take it over 5 seconds to boot the core. From a user experience perspective 5 seconds to see any boot up image/animation on screen after turn on is unacceptable.
So i was thinking of including a separate very cheap micro which can hold the master line for the first couple of seconds and provide the boot up image. It would then hand over the SPI bus to the main micro.
This of course is not the only use case of the smaller micro. I would also use it for all the backlight control. The larger micro might go into a sleep state and i would like for the smaller micro to still keep the display on. (So basically the main micro will simply tell the small micro what brightness to keep things on and a default brightness in case the main micro sleeps).
Is there any way i could hold the small micro as master for first 5 seconds and then let go to the main micro for the rest of the time (and as a bonus, hand it back to the small micro when the main micro goes into sleep)?