Re: Bench tests needed...

[Shannen Durphey <shannen@grolen.com>]

Ludis Langens wrote:
> 
> Shannen Durphey wrote:
> >
> > I'm curious about something.  Anyone who's got a bench ecm set up, I'd
> > like to know if you can set up the timing to get more than 90 degrees
> > advance.  I've been playing with a 749 and it seems like timing
> > passing 90 degrees gets reset to 0.  Anyone else see this?
> 
> No need for a bench test.  All the GM ECM code I've looked has computed
> the advance in essentially the same way.  They end up with a byte which
> represents the angle of advance (or retard) with the value 256 being 90
> degrees.  The time for 90 degrees of crank rotation is calculated
> elsewhere.  Then they do some math with these values to convert the
> angle of advance into the time domain.  This is then programmed into the hardware.

The spark timing value is sent to the hardware as a 16 bit value. 
Maximum advance and retard are also 16 bit values. I'd like to add
about 80 degrees offset to the timing calcs, and it looked like a
simple matter of adding it in right before the maximum advance check
is done.

> 
> So - once that byte overflows (which happens at 90 degrees), the timing
> will wrap around back to 0 degrees.
Ok, is this done in hardware or software?

> 
> Is this something to do with the DIS/dizzy conversion?
Yes.
Shannen
> 
> --
> Ludis Langens                               ludis (at) cruzers (dot) com
> Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
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