The Microcontroller Idea Book - Jan Axelson's Lakeview Research

Chapter 13
Listing 13-7. (page 1 of 2) Creates instructions to set, clear, and toggle Port
1, bit 0 in BASIC-52.
;example program for creating custom commands and instructions
in BASIC-52
;system must contain code memory from 2000h-2079h
tokentable equ 2100h ;start address, token table
vectortable equ 2200h ;start address, vector table
org 2002h ;5Ah at 2002h tells BASIC-52
db 5ah ;to call 2048h (see below)
org 2048h ;Set bit 45 to tell BASIC-52
;that custom commands or
setb 45 ;instructions have been
ret
;added
org 2078h ;stores starting address of
mov dptr,#tokentable token table
ret
org 2070h ;stores starting address of
mov dptr,#vectortable vector table
ret
org tokentable ;token table start address
db 10h ;first user-defined token
db “TGGP10" ;command or instruction name
;(must use all capital
;letters, beginning
;combination of letters
;must be unique)
db 0 ;end of token indicator
db 11h ;2nd user-defined token
db “SETP10" ;command or instruction name
db 0 ;end of token indicator
db 12h ;final user-defined token
db “CLRP10" ;command or instruction name
db 0ffh ;end of list indicator
234 The Microcontroller Idea Book