Hello lujia@dfmc.com.cn,
So let's talk about the switch block:

In this example you can see we have 1 selector (top Constant block - value 2) and 2 input signals (values 4 and 5). If we take a look at the mask of the switch block, we can see the Data port order is set to 1-based contiguous. This means the selector will have values between 1 and the number of data ports (in our case, 2). This works in the following way:
| Selector input | Switch block output |
|---|
| 1 | 4 |
| 2 | 5 |
If we would have have 0-based contiguous selected, the values would have been between 0 and 1 for the selector.
In your example, you only have 1 data port, and the order is set to 0-based contiguous. This means the selector can have values between 0 (starting position for 0-based indexing) and 0 (number of data ports - 1, that is 1-1=0). So this is why Simulink issues that error.
Let me know what you are trying to achieve with these switches and I can help.
Another thing I want to mention - I'm not sure where you took the UART configuration block, but you have to delete it and put it in the model again, because it is not linked with the one from within our library. I'm not sure what happened there.
Let me know if you're still facing issues with this.
Kind regards,
Razvan.