Xilinx Spartan-3E User Manual - Push-Button Switches
16
Spartan-3E Starter Kit Board User Guide
UG230 (v1.0) March 9, 2006
Chapter 2:
Switches, Buttons, and Knob
R
Push-Button Switches
Locations and Labels
The Spartan-3E Starter Kit board has four momentary-contact push-button switches,
shown in
. The push buttons are located in the lower left 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
and the associated
UCF appears 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.
shows how to specify a pull-down resistor within the
UCF. There is no active debouncing circuitry on the push button.
Figure 2-2:
UCF Constraints for Slide Switches
NET
"SW"
LOC
= "L13" |
IOSTANDARD
= LVTTL |
PULLUP
;
NET
"SW"
LOC
= "L14" |
IOSTANDARD
= LVTTL |
PULLUP
;
NET
"SW"
LOC
= "H18" |
IOSTANDARD
= LVTTL |
PULLUP
;
NET
"SW"
LOC
= "N17" |
IOSTANDARD
= LVTTL |
PULLUP
;
Figure 2-3:
Four Push-Button Switches Surround Rotary Push-Button Switch
UG2
3
0_c2_02_021206
BTN_WE
S
T
(D18)
BTN_EA
S
T
(H1
3
)
ROT_A: (K18)
ROT_B: (G18)
ROT_CENTER: (V16)
BTN_NORTH
(V4)
BTN_
S
OUTH
(K17)
Re
qu
ire
s
a
n intern
a
l p
u
ll-
u
p
Re
qu
ire
s
a
n intern
a
l p
u
ll-
u
p
Re
qu
ire
s
a
n intern
a
l p
u
ll-down
Rotary Pu
s
h Button
S
witch
Notes:
1. All BTN_* push-button inputs require an internal pull-down resistor.
2. BTN_SOUTH is also used as a soft reset in some FPGA applications.