
Chapter 2: Switches, Buttons, and Rotary Knob
R
NET
NET
NET
NET
"SW<0>"
"SW<1>"
"SW<2>"
"SW<3>"
LOC
LOC
LOC
LOC
=
=
=
=
"V8" |
"U10"|
"U8" |
"T9" |
IOSTANDARD
IOSTANDARD
IOSTANDARD
IOSTANDARD
=
=
=
=
LVCMOS33
LVCMOS33
LVCMOS33
LVCMOS33
;
;
;
;
Figure 2-2: UCF Constraints for Slide Switches
SUSPEND Switch
The SUSPEND slide switch, shown in Figure 2-3 , connects directly to the FPGA’s
SUSPEND input pin. If Suspend mode is enabled in the FPGA application, then the FPGA
enters Suspend mode whenever the switch is set to “SUSPEND.” If the switch is then
changed back to “RUN,” then the FPGA resumes operation from the state before it entered
Suspend mode. Likewise, if Suspend mode is enabled, then the AWAKE pin is reserved to
RUN
SUSPEND
UG334_c2_03_052407
Figure 2-3:
Suspend Switch
To enable Suspend mode, add the configuration string shown in Figure 2-4 to the user
constraints file (UCF). If Suspend mode is not enabled in the application, then the
SUSPEND switch has no affect on the design and the AWAKE pin is available as a general-
purpose I/O.
CONFIG ENABLE_SUSPEND = “ FILTERED” ;
Figure 2-4: UCF Constraints to Enable Suspend Mode
For more information on Suspend mode, see the following application note:
26
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XAPP480: Using Suspend Mode in Spartan-3 Generation FPGAs
UG334 (v1.1) June 19, 2008