Spartan-3A/3AN FPGA Starter Kit Board User Guide
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27
UG334 (v1.1) June 19, 2008
Push-Button Switches
R
Push-Button Switches
Locations and Labels
The Spartan-3A/3AN Starter Kit board has four momentary-contact push-button
switches, shown in
Figure 2-5
. The push buttons are located in the lower right corner of the
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
Figure 2-5
, and the
associated UCF is listed in
Figure 2-7
.
Operation
Pressing a push button connects the associated FPGA pin to 3.3V, as shown in
Figure 2-6
.
Use an internal pull-down resistor within the FPGA pin to generate a logic Low when the
button is not pressed.
Figure 2-7
shows how to specify a pull-down resistor within the
UCF. There is no active debouncing circuitry on the push button.
Figure 2-5:
Four Push-Button Switches Surround the Rotary Push-Button Switch
UG334_c2_05_052407
BTN_WEST
(U15)
BTN_EAST
(T16)
ROT_A:
(T13)
ROT_B:
(R14)
ROT_CENTER:
(R13)
BTN_NORTH
(T14)
BTN_SOUTH
(T15)
Requires an internal pull-up
Requires an internal pull-up
Requires an internal pull-down
Rotary Push Button Switch
Notes:
1. All BTN_* push-button inputs require an internal pull-down resistor.
Figure 2-6:
Push-Button Switches Require an Internal Pull-Down Resistor in the
FPGA Input Pin
UG230_c2_03_021206
BTN_* Signal
Push Button
3.3V
FPGA I/O Pin
Содержание Spartan-3A DSP FPGA Series
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