The LJMP and 0x800 load address issues are not really problems. Rather they are limitations of the tool set you have chosen to use. So there really is nothing you can do about it unless you make some changes to your setup. Here is a list of some of your options:

1) Purchase the full license Keil C51 tool set that does not have the above limitations.

2) Write your code in assembly language instead and make use of a free assembler toolset. One such is the assembler from

3) Search out a free compiler that works for 8051. One such is known as SDCC.

4) Convert away from using the 89C2051 to some other type that has more code FLASH and can accomodate the offsetted code start that is a characteristic of the free Keil tool set.

5) Purchase a low cost eval board from SiLabs (should be about 100$US) that comes with a board with MCU already mounted for you, a power module, a USB cable, the SiLabs downloader/debugging pod AND a CDROM with an eval version of the Keil compiler. This version of the Keil compiler comes with a different and less stringent set of limitations on the Keil tool set. In this case the SiLabs web says that the code limit is 4K bytes. The 2K offset is still there but should not be a problem since all the SiLabs MCUs that I am aware of have more than 2K of FLASH space.

Michael Karas