14
MicroBlaze Development Kit Spartan-3E 1600 Edition User Guide
www.xilinx.com
UG257 (v1.1) December 5, 2007
Chapter 2:
Switches, Buttons, and Knob
R
Push-Button Switches
Locations and Labels
The MicroBlaze Development Kit board has four momentary-contact push-button
switches, shown in
Figure 2-3
. 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
Figure 2-3
and the
associated UCF appears in
Figure 2-5
.
Operation
Pressing a push button connects the associated FPGA pin to 3.3V, as shown in
Figure 2-4
.
Use an internal pull-down resistor within the FPGA pin to generate a logic Low when the
button is not pressed.
Figure 2-5
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<0>" LOC = "L13" | IOSTANDARD = LVTTL | PULLUP ;
NET "SW<1>" LOC = "L14" | IOSTANDARD = LVTTL | PULLUP ;
NET "SW<2>" LOC = "H18" | IOSTANDARD = LVTTL | PULLUP ;
NET "SW<3>" LOC = "N17" | IOSTANDARD = LVTTL | PULLUP ;
UG257_02_060206
Figure 2-3:
Four Push-Button Switches Surround Rotary Push-Button Switch
UG257_02_0
3
_061
3
06
S
partan-
3
E
Development Board
Rot
a
ry P
us
h B
u
tton
S
witch
ROT_A:(K18) re
qu
ire
s
a
n intern
a
l p
u
ll-
u
p
ROT_B:(G18) re
qu
ire
s
a
n intern
a
l p
u
ll-
u
p
ROT_Center:(V16) re
qu
ire
s
a
n intern
a
l p
u
ll-down
BTN_NORTH (V4)
BTN_WE
S
T (D18)
BTN_
S
OUTH (K17)
BTN_EA
S
T (H1
3
)
Note
s
:
1. All BTN_* p
us
h-
bu
tton inp
u
t
s
re
qu
ire
a
n intern
a
l p
u
ll-down re
s
i
s
tor.
2. BTN_
S
OUTH i
s
a
l
s
o
us
ed
as
a
s
oft re
s
et in
s
ome FPGA
a
pplic
a
tion
s
