Hello,
After reading all that manuals and specifications, I decided to ask a general question.
In the datasheets, user guides that I read, generally there are two warnings for DIO:
-Do not connect digital outputs to circuits which drives current above limitations,
-Do not drive the line with voltages outside its operating range.
Talking in general, these tell me that I need to pay attention to current when dealing with outputs and to voltage when dealing with inputs. So I have that question, can I wire a power supply to digital inputs directly without exceeding its' normal operating range and without any protecting circuit? Actually in my feelings, this is not possible. But why some product documents clearly mention the internal impedance of inputs while others does not clearly indicate those? How can I decide if I can connect a signal directly to an input (for example USB-6525 indicates a current limiting circuit, but I can not see a clear explanation in datasheet of USB-6251)?