Xilinx Spartan-6 FPGA Series, User Manual

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Spartan-6 FPGA Power Management www.xilinx.com 23
UG394 (v1.1) September 4, 2012
Post-Configuration CRC Limitations When Using Suspend Mode
Several design options are possible:
1. Do not use the post-configuration CRC feature when the suspend mode feature is
enabled and vice versa.
2. Always reprogram the device when a CRC error occurs.
Table 1-7 summarizes the various bitstream options associated with suspend mode.
Table 1-7: Suspend Mode Bitstream Generator Options
Suspend Mode
Bitstream Options
Options
(Default) Description
drive_awake
No
(Default)
If suspend mode is enabled, indicates the present status on AWAKE using an
open-drain output. An external pull-up resistor or High signal is required to exit
SUSPEND mode.
Yes
If suspend mode is enabled, indicates the current status by actively driving the
AWAKE output.
en_sw_gsr No
(Default)
The state of all clocked primitives in the FPGA is preserved.
Yes
Pulses the GSR signal during wake-up, setting or resetting all clocked
primitives, as originally specified in the FPGA application. The GSR pulse
occurs before the AWAKE pin transitions High and before the
sw_gwe_cycle
and sw_gts_cycle settings are active.
sw_clk StartupClk
(Default)
Uses the clock defined by the
StartupClk
bitstream generator setting to
control the suspend wake-up timing.
InternalClk
Uses the internally generated 50 MHz oscillator to control the suspend wake-up
timing.
sw_gwe_cycle
1,..,5,...,1024
Default is 5
After the AWAKE pin is High, indicates the number of clock cycles as defined by
the
sw_clk setting, when the global write-protect lock is released for writable
clocked primitives (flip-flops, block RAM, etc.). The default value is five clock
cycles after the AWAKE pin transitions High. Generally, this value is equal to or
greater than the
sw_gts_cycle setting.
sw_gts_cycle
1,..,4,...,1024
Default is 4
After the AWAKE pin is High, indicates the number of clock cycles as defined by
the
sw_clk setting, when the I/O pins switch from their SUSPEND Attribute,
page 16 settings back to their normal functions. The default value is four clock
cycles after the AWAKE pin goes High. Generally, this value is equal to or less
than the
sw_gwe_cycle setting.
multipin_wakeup No
(Default)
Disables multi-pin wake-up.
Yes Enables multi-pin wake-up.
wakeup_mask
0x00
(Default)
Masks out SCP<7:0>
<hex string> FF
enables SCP<7:0>,
0F
enables SCP<3:0>.