Altera DE1-SoC - User Input;Output Devices (Buttons, Switches, LEDs)

DE1-SoC User Manual
23
www.terasic.com
March 14, 2014
3.6.1 User Push-buttons, Switches and LEDs
The board has four push-buttons connected to the FPGA, as shown in Figure 3-13 Connections
between the push-buttons and the Cyclone V SoC FPGA. Schmitt trigger circuit is implemented and act
as switch debounce in Figure 3-14 for the push-buttons connected. The four push-buttons named
KEY0, KEY1, KEY2, and KEY3 coming out of the Schmitt trigger device are connected directly to
the Cyclone V SoC FPGA. The push-button generates a low logic level or high logic level when it
is pressed or not, respectively. Since the push-buttons are debounced, they can be used as clock or
reset inputs in a circuit.
Figure 3-13 Connections between the push-buttons and the Cyclone V SoC FPGA
Pushbutton releasedPushbutton depressed
Before
Debouncing
Schmitt Trigger
Debounced
Figure 3-14 Switch debouncing
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