On 4/10/2012 9:56 AM, Steve Stallings wrote:
>> -----Original Message-----
>> From: Sebastian Kuzminsky [mailto:[email protected]]
>> Sent: Monday, April 09, 2012 6:02 PM
>> To: Enhanced Machine Controller (EMC)
>> Subject: Re: [Emc-users] Hal_parport and EPP
>>
>>      
> <snip>
>    
>> Simply switching the port to EPP mode doesn't accomplish anything.
>>
>>      
> Simply switching the port to EPP mode DOES accomplish
> one significant thing. Those outputs that are open collector
> with pull-ups in regular mode become Totem-Pole driven
> outputs when in EPP mode. This change is significant
> for the Gecko G540 which needs the extra drive current
> when the output is a logic one. The inputs to the G540
> are unbuffered optocoupler LEDs and there is no source
> of power on that side of the interface in the G540, so
> adding a buffer or additional pull-ups inside the G540
> is not possible.
>
> Steve Stallings
>
>
>
>    
Now the G540 circuitry makes sense.    I never thought about the optos.

Thanks for the clarification.

Dave


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