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Hacking up Honda's ECU
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PostPosted: Mon Aug 13, 2007 9:52 pm 
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Joined: Tue Jul 27, 2004 3:01 am
Posts: 2945
Location: Tampa bay, Florida
I was trying to further my understanding of asm code and came across a difference between the Nx_800 book and the code dasm'ed by Andy's program.

In the book it shows
CLR A as opcode "FA" (DD = 1)
and
CLRB A as opcode "FB" (DD = 0)
In the dasm it seems to be different..

CLRB A shows as opcode "FA" (DD = 0)
CLR A shows as opcode "F9" (DD = 1)

I assume the dasm is correct and the book is wrong..? (Since the ROMs are working with this 'bug'..)


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PostPosted: Tue Aug 14, 2007 3:20 am 
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Joined: Tue Jul 27, 2004 2:19 am
Posts: 653
Location: France
For nX-8/500S Core :

opcode "FA" (DD=1) = CLR A

opcode "FB" (DD=0) = CLRB A

opcode "FAxx" (DD=0) = LB A,#xx


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PostPosted: Tue Aug 14, 2007 9:40 pm 
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Joined: Tue Jul 27, 2004 3:01 am
Posts: 2945
Location: Tampa bay, Florida
So, does the 66201, 207,etc.. not really follow the Nx8_500s core?

My 273_stock ASM:
Code:
                CLRB    A                      ; 0064 0 208 ??? FA


Code:
                CLR     A                      ; 022C 1 3F0 ??? F9


Note how it shows the opcode for clrb A is FA not FB
and CLR A opcode is F9 not FA
This is why I'm confused..


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