There are two CPU cards pin to connect for I2C,UART,and other interface(3.3V CMOS).Two cards VCCIO can not power up simultaneously.Cause that another card vccIO is 1.23V before power on that voltage not a continuous slope .The current flows back to vccio. But cpu don't work Abnormally.Do I need to optimize the design？

 

One solution will be to use a fiber-optic data link between the two CPU boards. That will keep the power supplies totally isolated, and no power problems possible. Not a simple solution, but certainly it can provide the required isolation.

 

It is the internal board interconnection of the product.It's not long-distance communication between products. The fiber-optic data link is not allowed.I think this is a common problem between boards.

 

One solution will be to use a fiber-optic data link between the two CPU boards. That will keep the power supplies totally isolated, and no power problems possible. Not a simple solution, but certainly it can provide the required isolation.

It is the internal board interconnection of the product.It's not long-distance communication between products. The fiber-optic data link is not allowed.I think this is a common problem between boards.

 

In the profession of engineering it is often possible to come up with designs that can not be implemented. Requiring two different voltages from one source at the same time is an example of that being the case. The simple solution is for the loads to be separated and for separate regulation of the power for each load. That is one solution.
Another option that is also a solution is a re-design of the loads to use a common supply voltage but to internally control the output voltage.
A third option will be a re-design to avoid the use of such different voltages. That has been my choice over the years. Using a single, more common voltage also avoids the problem of using products with a short product availability life-time.