Sometime we will have the requirement to use Cpu Uart(debug port),most of the time the Uart want to connect a slave chip.But usually the slave chip usually will disturb the man chip start.There has some way to solve this issue.
1.Use a main chip's gpio to control the slave chip's power or reset pin.
In the main chip uboot stage,power off or keep reset the slave chip.when the system is complete started.Then power on the slave chip.Need to modify the uboot code or system code.
2.Use a special key to stop the uboot.
eg:<CTRL – C>,need to modify the uboot code.
3.Increase the Uboot delay to wait the slave chip complete started.
Need to modify the uboot code.Not suggested.