I can not change RDP

[kazu_robot]

Hello!

I am using a board equipped with STM32F205 VCT7.

https://www.hibot.co.jp/ecommerce/prod-detail/16

During "Connect" with STM32CubeProgrammer, I accidentally dropped the main power of the board.

Since then, such a screen came out when "Connect" was made.

I had a problem like this before, I sent the board to the company that made this board and inquired.

The company replied that "RDP was at Level 1, so I changed it to Level 0 with ST-LINK / V2 Utility."

I think this problem can be solved by changing RDP, and when I try to change RDP from "Option Byte", such a screen appears.

Why is RDP not changeable even though "Connect" is done?

Help me.

[Piranha]

Try setting Mode to Connect Under Reset.

[kazu_robot · Accepted solution]

Thank you for your reply.

This problem was caused by my mistake.

I used to supply power using a regulated power supply.

In some cases, a voltage lower than that required to drive the board is supplied.

This caused such a problem.

Thank you for thinking together.