Re: IIgs and call-151

[Dennis Jenkins <dennis@usb.com>]

Dave, you know way too much(tm) :)  I think it is safe to say that most
of us regulars in this group know too much.  So, as someone once asked,
when are you doing to write a comprehensive "Everything there is to know
about your IIgs" book? :)

David Empson wrote:
> 
> Jeff Blakeney <CUTjefbla@bconnex.net> wrote:
> 
> > On Thu, 04 Jan 2001 12:59:57 -0600, Dennis Jenkins <dennis@usb.com>
> > wrote:
> >
> > >     On my ROM1 GS, running either ProDOS or Dos3.3, I can not seem to use
> > >the monitor rom program correctly.  I expect "F819L" to disassemble the
> > >code that does HLIN.  The code that it displays has nothing to do with
> > >lowres graphics.  Yes when my assembly and C programs 'jsr $f819', HLIN
> > >is performed.
> >
> > When you get to the monitor prompt, instead of just typing F819L, type
> > FF/F819L.  That appears to be the code you are looking for.
> >
> > I have no idea why the code in 00/F819 is different from what is at
> > FF/F819.
> 
> The IIgs monitor has special support for the "language card" RAM
> ($D000-$FFFF).  This means that whenever you examine memory in banks 0,
> 1, $E0 or $E1 within this address range (using a memory dump or a
> disassembly), you will always see the language card memory, not the ROM.
> 
> There is also a special command to select the language card bank for
> monitor commands.  Without going and looking it up, I think it is 1=L
> and 0=L (case sensitive).  This selects between the two banks in the
> $D000-$DFFF area.  The $E000-$FFFF area only has one bank.
> 
> If you want to see the ROM code that would normally be accessed in these
> memory areas, you have to refer to it in bank FF (which is never
> switched out).
> 
> The G (go) command always restores the language card bank switching to
> the normal (or configured) state before calling the specified location.
> This means that you can safely call monitor or BASIC routines in bank 0
> (or call machine code programs which in turn make calls into the ROM).
> 
> Note that you can't use the G command unless the monitor's active bank
> is set to 0, because the G command always executes code starting out in
> emulation mode, and emulation mode cannot be used to run code outside of
> bank 0 (at least, not safely).  If you've just done FF/F819L, you will
> have to use 0/300G (or whatever) to call a routine in bank 0.

-- 
dennis@usb.com                           Universal Savings Bank.

The three most dangerous things are a programmer with a soldering
iron, a manager who codes, and a user who gets ideas.