After pressing reset buton, the code turns bootloader . How can i fix it?

[G_A.]

I am writing a custom bootloader that gets hex of new user code via usart and writing on flash.

Now the system jumps to another sector and the new code works. But after presing the reset buton, the system turns bootloader .How an I fix this problem?Thanks in advance.

(Btw I tried to load this new hex code on flash via ST-Link Utility. But I did not observe same problem)

[G_A.]

Thanks for your advices. I found the problem. Actually after reset, the turning back to bootloader is a normal situation. But I have should used a flag ikeeping inside information about if there is a new data coming via usart or not. Thus it will pass from bootloader to user app if there is no new data.

Do you know any flag showing if USART dma receive new data?