Thanks PB. I don't mind the rain. Where I live, rain is always welcome! Thanks for reminding me about the separation of internal RAM and internal eeprom memory. My thinking was that one could use internal eeprom to store a program (my "monitor program", residing inside the 4051 with start address 0000 and being smaller than 4KB) which, when the uP resets and start executing from adress 0000, would do the necessary initialising and start communicating with my PC enabling me to develop my own pgm directly in assembler (hex machine code - not mnemonics), store it in external RAM (made nonvolatile by battery backup) for transporting to a separate board. In this process the "monitor program" can of course branch to internal 128 byte RAM for temporary storage of variables and constants. This "monitor program" should enable me to interactively write my own little pgm using the PC's keyboard.