Chapter 2: Switches, Buttons, And Rotary Knob; Slide Switches; Locations And Labels; Operation - Xilinx spartan-3a User Manual

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Switches, Buttons, and Rotary Knob

Slide Switches

Locations and Labels

Operation

UCF Location Constraints

Spartan-3A/3AN FPGA Starter Kit Board User
UG334 (v1.1) June 19, 2008
®
The Spartan -3A/3AN FPGA 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.
SW3
(T9)
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.
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.
Guidewww.xilinx.com
SW2 SW1 SW0
(U8) (U10) (V8)
Figure 2-1: Four Slide Switches
Chapter 2
HIGH, '1'
LOW, '0'
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