Found.. 8051 FAQ.

[Ciciora Steve]

Craig Pugsley writes:

<8051 FAQ stuff deleted> 

>Now, back to an EFI question. 
> 
>This is what I plan to do to get it running: 
> 
>I'm going to just use a "3-D" look-up table, with RPM on one axis and
>load on the other (load being just engine vacuum level for starters).
>The location pointed to by RPM and load will be a number that is used
>for a counter that turns on the injectors: 
> 
>I plan to use 4 bits (=16 points) for the RPM axis and 5 bits (=32 
>points) for the load axis, giving a total of 512 settings - (Co 
>incidentally the same way that other well known controllers are laid 
>out). 
> 
>Once I get an engine to run then I'll start thinking about an 
>accelerator pump, cold starting, over-run cut off, altitude 
>compensation, 
>EGO correction etc etc etc. 
> 
>Does the 3D table sound described above sound like a reasonable 
>implementation? Has anyone tried something like this before? 
> 
>Craig. 
> 
 
  It sounds like your line of reasoning is very similar to mine!  I'm
working on some code to do 4 point linear interpolation for the fuel map.
My fuel map will take an 8 bit number (0->255) for the engine RPM and an
8 bit number for the engine load.  It will then output a number (8 bits?
16 bits?) proportional to the amount of fuel to inject.  My map will be
17 x 17 x 8 bit numbers.  Even though i will use the upper 4 bits (0->15)
for the lookup of the map, to get a point on either side of the 0->15 
number you need 17 points, hence the 17 x 17 map instead of 16 x 16.