Okay ... I think about your answers.

But soooo hard can't this are, I think.

To the EEPROM (or what ever) I write the
code as Intel Hex format.


I can do it like this:

a)
With the PC Software I load the code into the program (the pc software).

b)
Then I press "Upload" Button and the PC program
write the code as Intel Hex to maybe COM1.
The program think, at the other end is a 8052.

But it's a, maybe a EEPROM with shift
register.


Later, I would like to run the code:

a)
I turn off all power

b)
I switch the EEPROM, or the right one is alreday
inside

c)
After power on, the EEPROM would like copy
to the 8052, at Intel Hex of course.

On this time, the 8052 think, that the data
come from a PC ...

That's it !

Other considerations:
- between PC and EEPROM is a MAX233
- between EEPROM and 8052 too
- the EEPROM is on a little PCB (for easy change)