EP2S90F1020C5 Datasheet, PDF (584/768 Pages) Altera Corporation – Stratix II Device Handbook, Volume 1

Fast Passive Parallel Configuration
In multi-device FPP configuration, the first device’s nCE pin is connected
to GND while its nCEO pin is connected to nCE of the next device in the
chain. The last device’s nCE input comes from the previous device, while
its nCEO pin is left floating. After the first device completes configuration
in a multi-device configuration chain, its nCEO pin drives low to activate
the second device’s nCE pin, which prompts the second device to begin
configuration. All other configuration pins (nCONFIG, nSTATUS, DCLK,
DATA[7..0], and CONF_DONE) are connected to every device in the
chain. Pay special attention to the configuration signals because they may
require buffering to ensure signal integrity and prevent clock skew
problems. Ensure that the DCLK and DATA lines are buffered for every
fourth device.
When configuring multiple devices, configuration does not begin until all
devices release their OE or nSTATUS pins. Similarly, since all device
CONF_DONE pins are tied together, all devices initialize and enter user
mode at the same time.
Since all nSTATUS and CONF_DONE pins are tied together, if any device
detects an error, configuration stops for the entire chain and the entire
chain must be reconfigured. For example, if the first device flags an error
on nSTATUS, it resets the chain by pulling its nSTATUS pin low. This low
signal drives the OE pin low on the enhanced configuration device and
drives nSTATUS low on all devices, which causes them to enter a reset
state. This behavior is similar to a single device detecting an error.
If the Auto-restart configuration after error option is turned on, the
devices will automatically initiate reconfiguration if an error occurs. The
devices will release their nSTATUS pins after a reset time-out period
(maximum of 100 µs). When all the nSTATUS pins are released and pulled
high, the configuration device tries to reconfigure the chain. If the
Auto-restart configuration after error option is turned off, the external
system must monitor nSTATUS for errors and then pulse nCONFIG low
for at least 2 µs to restart configuration. The external system can pulse
nCONFIG if nCONFIG is under system control rather than tied to V_CC.
Your system may have multiple devices that contain the same
configuration data. To support this configuration scheme, all device nCE
inputs are tied to GND, while nCEO pins are left floating. All other
configuration pins (nCONFIG, nSTATUS, DCLK, DATA[7..0], and
CONF_DONE) are connected to every device in the chain. Configuration
signals may require buffering to ensure signal integrity and prevent clock
skew problems. Ensure that the DCLK and DATA lines are buffered for
every fourth device. Devices must be the same density and package. All
devices will start and complete configuration at the same time.
Figure 7–10 shows multi-device FPP configuration when both Stratix II or
Stratix II GX devices are receiving the same configuration data.
7–32
Stratix II Device Handbook, Volume 2
Altera Corporation
January 2008