ALDL codes & questions.

[TOM_HUSSEY at HP-Canada-om1.om.hp.com]

Hi,

Here is an update on a few things relating to the ALDL thread. First for
those who asked me for my homebrew disassembler there is a bug (much
shame). Please update the opcode file with the one attached . Still no
guarantee it's all fixed but I think....

I had a chance to look more at Peter's code, and found a few more things
that may be of interest. I fairly sure that the code here is for the
aldl write. Comments are my own as I understand the code.

****
* WRITE DATA TO ALDL
****
EC48  B7 40 0A    	STAA   $400A           ; WRITE DATA TO SCI
EC4B  BB 01 4B    	ADDA   $014B           ; ADD DATA TO CHECKSUM
EC4E  B7 01 4B    	STAA   $014B           ; SAVE NEW CHECKSUM
EC51  7C 01 4A    	INC    $014A           ; UPDATE POINTER
EC54  20 16       	BRA    $EC6C           ; RETURN

I have been tracing back from there and suggest that the table located
at $8882 through $8977 is formatted as pointer:id byte. These form a
link list (I think) see this code. Again comments are my own not for
sure what the code is.

EA41  CE 88 82    	LDX    #$8882          ; POINTER TO TABLE FORMAT 
                                               ; IS POINTER:ID

EA44  A1 02       	CMPA   $02,X           ; READ THE BYTE FOLLOWING 
EA46  27 06       	BEQ    $EA4E           ; IF TABLE ID = ID...

EA48  EE 00       	LDX    $00,X           ; ELSE NEXT ADRS IN CHAIN
EA4A  26 F8       	BNE    $EA44           ; IN THE CHAIN. LOOP TILL 

EA4C  20 5F       	BRA    $EAAD           ; END OF CHAIN IS HIT...

I hope this is a help.

I looked a bit more at the port on my 97 Camaro Z28. The sequence the
ECM uses on my car to change direction of the ALDL to input is

91 59 00 00 00 00 16

Once we get a bit closer to the code that needs to be sent, I will work
on exact timing but it looks quite loose (see my earler post with aprox
timing). 

Sorry for the long post. See you later -Tom Hussey