It’s because of some kind of problem at using SCK and DIO ports of MCU. After flashing a program it’s no longer can be used as SWD. I’ve erased chip with attaching a hardware button to reset state pin and gnd. Than I go to “right click on a project -> Target -> erase chip...” Finally just before erase start I’ve pressed hardware button and released it. It works. Chip erased and ready just for one more debug. After that it’s no longer able to use SWD. I’s not very comfortable to do so after every debug, But my chineese version of ST-Link v2 dongle doesn’t use reset pin. The voltage level on it stay’s the same at any kind of debuger settings such as “connect under reset”, software or hardware reset either. I’m looking for solution right now.