7730 memory locations

[jsg at mrcday.com]

I've looked through the archives, and have not found a description of
memory locations 0x3128-0x3129 and 0x30BD-0x30BE in the 7730. They are
reported as the spark advance through the ALDL, but it's not clear to
me how they are formed, why they differ by the initial timing _and_
knock sensor retard, and which value the engine is really using when
different. Does anyone know? (I need to build one of Bruce's ECM test
benches...) 

john gwynne