Boot.sel=0. Now is "Stopping Jumping to Image" impossible. How to reset boot-loader into default parameters value?

After changing boot.sel=0 into 1 over serial port, now it is not possible to stop loading to WinCE. It seems Boot-loader is set using some GPIO to stop loading process to windowsCE. We do not know, which GPIO is set as default in Boot-Loader.
before using boot.sel=1, we were be using serial port to stop starting windows, now it is not possible anymore.
At the moment pushing on [SPACE] does not effect anything in boot loader via serial port!

How can we reset Boot-Loader into default parameters, so that we stop Module T30 before jumping to image using serial port again?

Thank you in advance.

If you device still boots correctly and you are able to load any application, use the Config Block Editor to change the setting again. See also this developer website entry. If you have disabled explorer, copy the Config Block Editor into a folder AutoRun on a USB device so it gets loaded automatically after inserting the stick.

If you are not able to launch the application you could use the recovery mode to do a factory reset. More details on that here.