XRoar with GDB with HD6309

Hardware Hacking, Programming and Game Solutions/Cheats
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pser1
Posts: 1211
Joined: Sun Mar 25, 2012 7:32 pm
Location: Barcelona (SPAIN)

XRoar with GDB with HD6309

Post by pser1 » Sun Dec 02, 2018 10:48 pm

Hello Ciaran,
I wanted to give a chance to the games I am converting to take advantage of any HD6309 installed in place of the std MC6809
The code is fairly simple:

Code: Select all

Set6309	fcb   $10,$86,$55,$55		; ldw	#$5555
			fcb   $1f,$61					; tfr	w,x
			cmpx  #$ffff					; did it fail?
			beq   ES6309					; yes, skip next
			fcb   $11,$3d,$01	     		; ldmd  #$01
ES6309 	rts								; return
As the movement in the games is synced to VSync, I am not expecting more speed but better smoothness
So I cannot tell if it works well because on my Real Dragon64 it works and no problems arise ...
Then I decided to trace this code with GDB and much to my surprise the registers are not correctly updated.
After the first LDW #$5555 register E (high byte) shows $00 and at its right the decimal value ... 21760 ($5500)
the low register, reg F shows value $00 too
Till now register md shows $00 but after the TFR W,X I can see clearly that register X has been loaded with #$5555 as I expected
and suprisingly register md now shows $55 (something's been shifted?)
The compare fails, so no branch is taken and then the LDMD #01 should put the 6309 into native mode
but md keeps showing value $55
I am afraid that there could be misaligned data in the interface XRoar - DBG ...
cheers
pere

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