Date   : Mon, 10 Apr 2006 02:58:58 +0100
From   : Rob <robert@...>
Subject: Re: [Fwd: Re: Contikit anyone?]

At 22:41 09/04/2006, dominic beesley wrote:


>The trouble is getting calling between different ROMS to work. I don't
>think my original posting was clear. I need to call between several
>different roms and each rom needs to call the OS. What is the correct
>way of making sure the OS reselects my ROM? I've tried poking &f4 but
>the OS seems to ignore this and returns back into the ROM I've got
>selected as the language.

OK..

&f4 is (or should be) always a copy of what the OS thinks is the 
"current" ROM, i.e. the last value written to ROMSEL (which is 
write-only) but only on the B's - I think the Master stores this 
elsewhere.  You shouldn't manipulate this directly as you can really 
confuse things.

I suspect you may have to designate one ROM as the language, which is 
the main one to have control, and have the others as service ROMs, 
offering subroutines via a service call (called via OSBYTE &8F from 
the language).  This way you don't actually need to know what socket 
a service ROM is in, or even which ROM any particular service is 
handled by, either.

Of course, you can also use a service call to tell a ROM to establish 
an extended vector pointing into itself for later use by other 
routines.  (service calls are entered with X containing the current 
ROM number, so it's easy.)  I've done this in the past, to make a ROM 
intercept OSBYTE/OSWORD, etc, so it should work.


Rob