Altera Corporation
7–59
January 2008
Stratix II Device Handbook, Volume 2
Configuring Stratix II and Stratix II GX Devices
pins will no longer have weak pull-up resistors and will function as
assigned in your design. Enhanced configuration devices and EPC2
devices drive DCLK low and DATA0 high at the end of configuration.
If an error occurs during configuration, the device drives its nSTATUS pin
low, resetting itself internally. Since the nSTATUS pin is tied to OE, the
configuration device will also be reset. If the Auto-restart configuration
after error
option, available in the Quartus II software, from the General
tab of the Device & Pin Options dialog box is turned on, the device
automatically initiates reconfiguration if an error occurs. The Stratix II
and Stratix II GX devices release the nSTATUS pin after a reset time-out
period (maximum of 100 s). When the nSTATUS pin is released and
pulled high by a pull-up resistor, the configuration device reconfigures
the chain. If this option is turned off, the external system must monitor
nSTATUS
for errors and then pulse nCONFIG low for at least 2 s to restart
configuration. The external system can pulse nCONFIG if nCONFIG is
under system control rather than tied to VCC.
In addition, if the configuration device sends all of its data and then
detects that CONF_DONE has not gone high, it recognizes that the device
has not configured successfully. Enhanced configuration devices wait for
64 DCLK cycles after the last configuration bit was sent for CONF_DONE to
reach a high state. EPC2 devices wait for 16 DCLK cycles. In this case, the
configuration device pulls its OE pin low, driving the target device’s
nSTATUS
pin low. If the Auto-restart configuration after error option is
set in the software, the target device resets and then releases its nSTATUS
pin after a reset time-out period (maximum of 100 s). When nSTATUS
returns to a logic high level, the configuration device tries to reconfigure
the device.
When CONF_DONE is sensed low after configuration, the configuration
device recognizes that the target device has not configured successfully.
Therefore, your system should not pull CONF_DONE low to delay
initialization. Instead, use the CLKUSR option to synchronize the
initialization of multiple devices that are not in the same configuration
chain. Devices in the same configuration chain will initialize together if
their CONF_DONE pins are tied together.
1
If you are using the optional CLKUSR pin and nCONFIG is pulled
low to restart configuration during device initialization, you
need to ensure that CLKUSR continues toggling during the time
nSTATUS
is low (maximum of 100 s).
When the device is in user-mode, pulling the nCONFIG pin low initiates
a reconfiguration. The nCONFIG pin should be low for at least 2 s. When
nCONFIG
is pulled low, the device also pulls nSTATUS and CONF_DONE
low and all I/O pins are tri-stated. Because CONF_DONE is pulled low, this