Chapter 9: Configuration, Design Security, and Remote System Upgrades in the Cyclone III Device Family
Configuration Features
9–9
When the device exits POR, all user I/O pins continue to tri-state. The user I/O pins
and dual-purpose I/O pins have weak pull-up resistors that are always enabled (after
POR) before and during configuration. After POR, the Cyclone III device family
releases
nSTATUS,
which is pulled high by an external 10-k pull-up resistor and
enters configuration mode.
When
nCONFIG
goes high, the device exits reset and releases the open-drain
nSTATUS
pin, which is then pulled high by an external 10-kpull-up resistor. After
nSTATUS
is
released, the device is ready to receive configuration data and the configuration stage
begins.
Cyclone III LS devices are accessible by limited JTAG instructions after POR. For more
information about enabling full JTAG instructions access, refer to
f
For more information about the value of weak pull-up resistors on the I/O pins that
are on before and during configuration, refer to the
and
chapters.
Configuration
Configuration data is latched into the Cyclone III device family at each
DCLK
cycle.
However, the width of the data bus and the configuration time taken for each scheme
are different. After the device receives all the configuration data, the device releases
the open-drain
CONF_DONE
pin, which is pulled high by an external 10-kpull-up
resistor. A low-to-high transition on the
CONF_DONE
pin indicates that configuration is
complete and initialization of the device can begin. The
CONF_DONE
pin must have an
external 10-k pull-up resistor for the device to initialize.
You can begin reconfiguration by pulling the
nCONFIG
pin low. The
nCONFIG
pin must
be low for at least 500 ns. When
nCONFIG
is pulled low, the Cyclone III device family is
reset. The Cyclone III device family also pulls
nSTATUS
and
CONF_DONE
low and all I/O
pins are tri-stated. When
nCONFIG
returns to a logic-high level and
nSTATUS
is released
by the Cyclone III device family, reconfiguration begins.
Configuration Error
If an error occurs during configuration, the Cyclone III device family asserts the
nSTATUS
signal low, indicating a data frame error, and the
CONF_DONE
signal stays low.
If the
Auto-restart configuration after error
option (available in the Quartus II
software from the
General
tab of the
Device and Pin Options
dialog box) is turned
on, the Cyclone III device family releases
nSTATUS
after a reset time-out period (a
maximum of 230
s),
and retries configuration. If this option is turned off, the system
must monitor
nSTATUS
for errors and then pulse
nCONFIG
low for at least 500 ns to
restart configuration.
August 2012
Altera Corporation
Cyclone III Device Handbook
Volume 1
ALTERA [ ALTERA CORPORATION ]
