Push-Button Switches; Locations And Labels; Operation - Xilinx Spartan-3A User Manual

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Push-Button Switches

Locations and Labels

The Spartan-3A/3AN Starter Kit board has four momentary-contact push-button
switches, shown in
board and are labeled BTN_NORTH, BTN_EAST, BTN_SOUTH, and BTN_WEST. The
FPGA pins that connect to the push buttons appear in parentheses in
associated UCF is listed in

Operation

Pressing a push button connects the associated FPGA pin to 3.3V, as shown in
Use an internal pull-down resistor within the FPGA pin to generate a logic Low when the
button is not pressed.
UCF. There is no active debouncing circuitry on the push button.
Spartan-3A/3AN Starter Kit Board User Guide
UG334 (v1.0) May 28, 2007
Figure
BTN_NORTH
BTN_WEST
(U15)
BTN_SOUTH
Notes:
1. All BTN_* push-button inputs require an internal pull-down resistor.
Figure 2-5: Four Push-Button Switches Surround the Rotary Push-Button Switch
Figure 2-7
Push Button
3.3V
Figure 2-6: Push-Button Switches Require an Internal Pull-Down Resistor in the
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2-5. The push buttons are located in the lower right corner of the
Figure 2-7.
Rotary Push Button Switch
ROT_A: (T13)
ROT_B: (R14)
(T14) ROT_CENTER: (R13)
(T15)
shows how to specify a pull-down resistor within the
FPGA I/O Pin
FPGA Input Pin
Push-Button Switches
Figure 2-5, and the
Requires an internal pull-up
Requires an internal pull-up
Requires an internal pull-down
BTN_EAST
(T16)
UG334_c2_05_052407
Figure
BTN_* Signal
UG230_c2_03_021206
2-6.
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