Some months have passed and I'm still stuck at getting the UART bootloader to respond.

I have the T89C51CC02 working - I can use a Galep-4 programmer to flash some firmware and the bootloader. (I had both FM0 and FM1 enabled for programming and simply did drag my test firmware and the uart bootloader hexfiles onto the data buffer. While programming the address counter did reach the F800 and above.)

Working tests include: LED blinker and serial communications

Most pins are not connected to anything, I have power, reset circuit, RS232 via MAX232CPE and a lone lowcurrent LED on P1.0.
I can tie P1.0 to GND via a switch (for the supposed factory boot condition) but I can't get the bootload to respond.

Using Galep-4 I have the following settings:
BLJB NOT enabled - Galep asks to enable, I assume it has to be disabled to work from reading the data sheet. (It doesn't ask for "1" or "0", just says "enable?" and allows to check the box.)
The port conditions seem to be the factory defaults which means I haven't changed them - P1_CF=FEh, P3_CF=FFh and P4=FFh

The datasheet says at page 5 that P1 has internal pullups - this means for the hardware condition that any pin that is not connected at all should read as "1" so for the moment I didn't connect anything there. P1.0 is tied to GND via a switch. From this arrangement I assume that P1 reads as FEh on boot if I tie P1.0 to ground. This corresponds to the factory default of the boot condition.
However it does not work!

I seem to either miss something or I completely do not understand something vital.

I know asking for working examples is not well received here but I'd be glad if someone could show me a schematic of a working design for this so that I can check what is different on my board

cheers,
Matthias