Xilinx Spartan-3A FPGA User Manual page 26

R
Switches, Buttons, and Rotary Knob
Slide Switches
Locations and Labels
The Spartan™-3A FPGA Starter Kit board has four slide switches, as shown in
The slide switches are located in the lower right corner of the board and are labeled SW3
through SW0. Switch SW3 is the left-most switch, and SW0 is the right-most switch.
Operation
When in the UP or ON position, a switch connects the FPGA pin to 3.3V, a logic High.
When DOWN or in the OFF position, the switch connects the FPGA pin to ground, a logic
Low. The switches typically exhibit about 2 ms of mechanical bounce. There is no active
debouncing circuitry, although such circuitry could easily be added to the FPGA design
programmed on the board.
UCF Location Constraints
Figure 2-2
assignment and the I/O standard used. The PULLUP resistor is not required, but it defines
the input value when the switch is in the middle of a transition.
Spartan-3A FPGA Starter Kit Board User Guide
UG330 (v1.3) June 21, 2007
SW3 SW2
(T9) (U8)
Figure 2-1: Four Slide Switches
provides the UCF constraints for the four slide switches, including the I/O pin
www.xilinx.com
SW1 SW0
(U10) (V8)
UG330_c2_01_021507
Chapter 2
Figure 2-1.
HIGH, '1'
LOW, '0'
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