7256 - How do we know the rise and fall time requirement for GPIO in FPGA?
Description :
There is no such specification given for GPIO rise and fall time.
Here are some general guidelines for GPIO in FPGA in general:
1. When dealing with faster rise/fall time, user needs to make sure it does not cause reflection and create signal integrity issue. If the rise time is too quick, it may cause signal overshoot and longer settling time as well especially at higher operating voltage.
2. When dealing with slower rise/fall time, it is determined by how clean the edge is. If the edge is clean, it allows the rise/fall time to be slower, but if it carries some noise, it would cause the input stage to toggle and thus require the rise/fall time to be faster.
It is recommended to apply noise filtering on both input signal and VCCIO power supply for clean edge.
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