Re: IIgs and call-151

[Rubywand <rubywand@my-deja.com>]

Dennis Jenkins <dennis@usb.com> writes ...

> Hello.
> 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.
> However, from inside the monitor, I can do a "c500g" or "c600g"
> to reboot the either my 3.5" or 5.25" drives.
>I think (I don't exactly remember) that I can do a "f819g"
> and HLIN will execute correctly
> (assuming the registers happen to hold good code.

     Right. Even though the F8xx code you see has nothing to do with
monitor code, doing a GO to some monitor routine at F8xx or running some
piece of code you type in which does a JSR to a monitor routine will
work.

>
> I assume the "call-151" does not put my
> IIgs into 6502/IIe mode, but into 65816/IIgs mode.
> Is this correct?

     Actually, the IIgs will be in //e "emulation mode" when you do a
CALL -151; and, you will still be in that mode when you arrive in the
monitor. (Even in this mode, you can still execute typed-in routines
using most 65C816 op codes.)


> Either way, how do I get the
> monitor to show me the ROM code that I except?
>
 ....

     Since the monitor ROM in the IIgs is in Bank FF, Jeff B's approach
(listing code at FF/F8xx ...) is a way.


     The confusing thing about this business is that the IIgs is set up
to act like the monitor ROM is in Bank 00 whenever it thinks you are
doing 8-bit Apple II stuff (like when you access a monitor routine while
in the monitor or are running a BASIC program).

     On the other hand, it drops the pretense when it comes to viewing
memory under the monitor. There is no ROM in Bank 00. So, when you do an
F800L, you end up looking at part of Bank 00 'Language Card' RAM.



Rubywand


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