Ray Henry wrote:
> Hi Eric
> 
> I've tried all sorts of things with this problem of unknown pin
> condition during PC start and stop and came to the personal conclusion
> that there is nothing short of a charge pump that I can be absolutely
> certain of.  
> 
I went to great lengths in my boards to prevent this kind of 
problem.  The outputs can only be enabled when the E-stop 
circuit is in the OK mode.  There is a watchdog timer that 
command an E-stop if the computer is not updating the board
continuously.  And, there is a power-on reset that puts it in 
E-stop.

When EMC starts up, it begins writing new velocity commands (of 
zero when it is not yet in "machine-on" state) to the board. 
That satisfies the watchdog timer, so then EMC can call for it 
to come out of E-stop.

Jon

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