[Gmecm] RE: More '730/$8D tuning questions...

[dozierhc at aol.com]

Clair Wrote:
 
3) I'm ASSuming that the TunerProRT software is placing the code at the
correct offset in the chip memory, as I have run the engine on both burned
chips and the OEM memcal.  I don't know what you mean by "absolute
addressing".

Clair...
 
Best way to explain absolute versus relative addressing is to look at your 27C256 EPROM used for the $8D SW and calibration.
 
When you burn the EPROM, you start at EPROM memory location $0000.  And the calibration and code goes up from there to the $FFFF location, which is the end of the Interrupt Vector Table.
 
BUT....The SW memory as addressed by the GM 68HC11 processort addresses this "$0000" location at $8000.
Hence the reason the addresses are all $8000 => $FFFF in the SW code.  This is becaues the address lines to reference the EPROM point to $8000 to enable the Chip Select line (CS).  So when the processor Program Counter points to lets say $E000, the memory decode points to the correct instruction in EPROM memory.  As a 27256 is a 32Kx8 memory, this mean its address locations run from $0000 to $7FFF, or 8192 bytes of memory.  So $E000 Micro address decodes to $6000 as the address on the EPROM.  But to resolve BRANCHes, JUMPs and CALLs , the assembler uses the Micros addressing logic.
 
So the ABSOLUTE memory address start is $8000 for the 32K EPROM, but it RELATIVE address is $0000 on the chip.
Or a ZERO offset on the chip for the start of the calibration and therefore cascading the SW alogtithms.
 
Hope this makes sense.  You need both to match for the EPROM code to work correctly.
 
BTW...You can set IC offsets in the TunerproRT to accomodate a lot of stuff.  Make sure in your Preferences for the XDF files that the Offset is set to ZERO (neither a -$xxxx or a positive $xxxx) so that it does not adress adjust the code.
 
Hank
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