On 2/18/2018 8:33 PM, Richard Thornton wrote:
> Actually I found a post from Charles Steinkuehler saying that it isn't a 
> 74CBTLV3861 it's a SN74CBTD3861DW which seems to add level shifting, I 
> think the G540 is tolerant of 3.3 or 5v?

The chips serve to limit the voltage seen by the FPGA on input
signals.  Basically, any signal from 0.0V to 3.3V passes through
unchanged, while signals above 3.3V will be 'clipped' to 3.3V.

So that works well for inputs from things like 5V encoder or limit
switch signals, but any outputs from the FPGA will still only be 3.3V.

Whether the 3.3V is enough to drive your motor controllers will depend
on the specific model, but most are setup for a 5V-12V input signal
driving the LED in the optoisolator.

-- 
Charles Steinkuehler
char...@steinkuehler.net

-- 
website: http://www.machinekit.io blog: http://blog.machinekit.io github: 
https://github.com/machinekit
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