Terasic Altera DE3, User Manual

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DE3 User Manual
13
2.3 Using the User I/O Interface
Push-Button Switches:
The DE3 board provides four user-defined, one CPU reset, and one Reconfigure push-button
switches. The Reconfigure push-button is used to force a re-boot of the FPGA from the serial
configuration device.
The CPU reset push-button is an input to the Stratix III device. It is intended to be the master
reset signal for the FPGA designs loaded into the Stratix III device. The CPU reset push
-button is connected to the DEV_CLRn pin on the FPGA. The DEV_CLRn setting is a pin
option in the Quartus II software that users must enable to function the CPU reset as
DEV_CLRn instead of a standard I/O.
Each of these switches is de-bounced using a Schmitt Trigger circuit, as indicated in Figure
2.7. Each push-button provides a high logic level (3.3 volts) or a low logic level (0 volts)
when it is not pressed or pressed, respectively. Table A-1 shows the connections between the
push-buttons and the FPGA.
Push Push Push Push----button depressed button depressed button depressed button depressed
Before
Before Before
Before
Debouncing Debouncing Debouncing Debouncing
Schmitt Triger Schmitt Triger Schmitt Triger Schmitt Triger
Debounced
Debounced Debounced
Debounced
Push Push Push Push----button released button released button released button released
Figure 2.7. Switch debouncing
Slide Switches and DIP Switch
There are also four slide switches and one 8-position DIP switch on the DE3 board. Each
switch is connected directly to a pin of the Stratix III FPGA. When a slide switch is in the
DOWN position (i.e., closest to the edge of the board) or the UP position, it provides a low
logic level (0 volts) or a high logic level (3.3 volts) to the FPGA, respectively. For 8-position
DIP switch, when a switch is in the DOWN position (closest to the edge of the board) or the
UP position, it provides a high logic level (3.3 volts) or a low logic level (0 volts) to the FPGA.
The connections between the slide switches and the FPGA are shown in Table A-2, whereas
Table A-3 shows the connections between the 8-position DIP switch and the FPGA.
RGB LEDs
There are 8 RGB user-controllable LEDs on the DE3 board. Each LED has red, green, and