Digilent 410-087P-KIT - Manual (Page 15)

Spartan-3E Starter Kit Board User Guide www.xilinx.com 15
UG230 (v1.0) March 9, 2006
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Chapter 2
Switches, Buttons, and Knob
Slide Switches
Locations and Labels
The Spartan-3E Starter Kit board has four slide switches, as shown in Figure 2-1 . 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 and 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 provides the UCF constraints for the four slide switches, including the I/O pin
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.
Figure 2-1: Four Slide Switches
UG230_c2_01_021206
LOW
HIGH
SW3
(N17)
SW2
(H18)
SW1
(L14)
SW0
(L13)