G'day,

I believe that there is a table driven cross assembler you get from the net.
It is sharware and it includes tables for both the 8051 and 8048 ( which I think is the ROM version of the 8039- they share the same instruction set anyway).
The program is called TASM ( not to be confused with Borland's Tasm)and can be obtained from:
Speech Technology Inc
Software Division
837 Front St South
Issaquch WA 98027 USA

regards,
Peter Rolls