SoCKit User Manual
21
www.terasic.com
December 1, 2015
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This section describes the interfaces to the FPGA. Users can control or monitor the different interfaces with user
logic on the FPGA.
3.6.1
User Push-buttons, Switches and LED on FPGA
The board provides four push-button switches connected to FPGA as shown in
Figure 3-11
. Each of
these switches is debounced using a Schmitt Trigger circuit, as indicated in
Figure 3-12
. The four
outputs called KEY0, KEY1, KEY2, and KEY3 of the Schmitt Trigger devices are connected
directly to the Cyclone V SoC FPGA. Each push-button switch provides a high logic level when it
is not pressed, and provides a low logic level when depressed. Since the push-button switches are
debounced, they are appropriate for using as clock or reset inputs in a circuit.
Figure 3-11 Connections between the push-button and Cyclone V SoC FPGA
Pushbutton released
Pushbutton depressed
Before
Debouncing
Schmitt Trigger
Debounced
Figure 3-12 Switch debouncing
