[Coco] Modifying Level1/coco1 for 6309 native mode

[Robert Gault]

Since there have been requests for this and the challenge is interesting, I've 
been looking at this problem. Here are initial results.

1) LWTools port of NitrOS-9 used for testing.
2) All level1/coco1 pertinent makefiles modified, for example

AFLAGS		+= -I$(LEVEL1)/modules

changed to

AFLAGS		+= -I$(LEVEL1)/modules -DH6309=1

or

AFLAGS		+= -DH6309=1

added. This will be necessary for defs, cmds, modules, and kernel.
The main coco1 makefile was modified:
CPU=6309
AFLAGS += -DH6309=1

Make sure that $(AFLAGS) gets added as needed to the makefiles or the H6309 will 
be ignored.

3) It was necessary to modify level1/modules/rel.asm as native mode was not 
initiated soon enough in level1, even though this source code is used for Level2 
6309 and already contains one LDMD #$03.

start1   orcc  #IntMasks  turn off IRQ's
          clr   >PIA0Base+3 turn off SAM IRQ's
          clra             make A=0 for later
          IFNE  H6309
          tfr   0,dp       set direct page to $0000
          ldmd  #3         native mode       !!!!!!!!!!!!!! new line

Start    clr   PIA0Base+3

          IFNE  (tano+d64+dalpha)
          clr   PIA0Base+1		added for Dragon, works on CoCo
          ENDC
          IFNE  H6309         !!!!!!!!!!!!!!! 3 new lines
          ldmd  #3                  native mode
          ENDC

With the above changes, the boot process proceeds much father than without the 
changes. The boot process without rel changes crashed at the first F$Link call.

The best way to test progress is with the MESS debugger. Use a version of MESS 
that correctly handles coco emulation. Start coco3h (6309) emulation, as that 
gives you the 6309 cpu and will run normal Level1 coco1 Nitros-9. Turn on the 
MESS debugger and set a breakpoint at $2602. Enter the DOS command with your 
test disk and the debugger will start as soon as rel starts running.
You should then tell MESS to start a trace, ex. trace 6309.log, and then leave 
the debugger. The text file 6309.log will be generated which will make it easy 
to spot where the boot process is crashing.
You can do the same thing with a normal coco1 6809 disk and compare a 6809.log 
vs your 6309.log.

It would make things much easier if there are other programmers interested 
enough to try this. We can compare notes and ideas. That could make Level1 6309 
native mode a reality.

Robert