CSCI E-93: Application Note 1

Dealing with DE2-115 Current Strength and Slew Rate
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Some output pins of the FPGA on the DE2-115 may produce the following
warning:

  Warning (15714): Some pins have incomplete I/O assignments. Refer to the I/O
  Assignment Warnings report for details

The I/O Assignment Warnings report is accessed by following these menus:
  Processing -> Compilation Report
    then
  Fitter -> Resource Section -> I/O Standards Section -> I/O Assignment Warnings

For example, buttonToLED will produce this warning even though pin
assignments were made in the .vhd (for a DE2-115) file using:

  attribute chip_pin: string;
  attribute chip_pin of led1: signal is "H15";
  attribute chip_pin of led2: signal is "G16";
  attribute chip_pin of pb1: signal is "R24";
  attribute chip_pin of pb2: signal is "N21";

This is because the warning was caused by issues with the default
Current Strength and Slew Rate.

For some information, see
https://www.altera.com/support/support-resources/knowledge-base/solutions/rd03312014_182.html
"Is it safe to ignore incomplete I/O assignment warning messages in
the Quartus II software for Active Parallel configuration pins?"

You can remove the warnings by changing the default selection of
"Current Strength" as "8mA (default)" and "Slew Rate" as "2 (default)"
in the Quartus II Pin Planner to "8mA" and "2 (fastest)",
respectively.

These can also be set in VHDL code using attribute name
altera_attribute as follows:

  attribute altera_attribute: string;
  attribute altera_attribute of led1: signal is "-name current_strength 8mA; -name slew_rate 2";
  attribute altera_attribute of led2: signal is "-name current_strength 8mA; -name slew_rate 2";