Date   : Sat, 08 Apr 2017 17:03:49 +0100
From   : jgh@... (J.G.Harston)
Subject: Making a new language ROM from scratch

Essentially, your ROM type needs to be %11xx0010 to indicate '6502 
code', your entry point is at 8000 which should JMP to your main code 
where you must initialise the stack, LDX #&FF:TXS and claim BRKV at 
&0202/3. You then own zero page from &00 to &8F, main memory from &400 
to &7FF and user memory from OSBYTE &83 to OSBYTE &84. You must talk to 
the system via the API calls at &FFCE to &FFF7.

You also need a method of selecting your language, so you need at 
minimum a *command service handler to recognise your selection command 
and tell the MOS to enter yourself. There is a sample minimal *command 
selection routine on the Wiki which uses the ROM's title as its 
selection command: 
http://beebwiki.mdfs.net/Simple_ROM_selection_command_code

-- 
J.G.Harston - jgh@...      - mdfs.net/jgh