Chapter 9: Configuration, Design Security, and Remote System Upgrades in the Cyclone III Device Family
9–37
Configuration Features
In a multi-device PS configuration, the nCEpin of the first device is connected to GND
while its nCEOpin is connected to the nCEpin of the next device in the chain. The nCE
input of the last device comes from the previous device, while its nCEOpin is left
floating. After the first device completes configuration in a multi-device configuration
chain, its nCEOpin drives low to activate the nCEpin of the second device, which
prompts the second device to begin configuration. The second device in the chain
begins configuration in one clock cycle. Therefore, the transfer of data destinations is
transparent to the external host device. All other configuration pins (nCONFIG
,
nSTATUS, DCLK,
DATA[0], and CONF_DONE) are connected to every device in the chain.
Configuration signals can require buffering to ensure signal integrity and prevent
clock skew problems. Ensure that the DCLKand DATAlines are buffered. Because all
device CONF_DONEpins are tied together, all devices initialize and enter user mode at
the same time.
If any device detects an error, configuration stops for the entire chain and the entire
chain must be reconfigured because all nSTATUSand CONF_DONEpins are tied together.
For example, if the first device flags an error on nSTATUS, it resets the chain by pulling
its nSTATUSpin low. This behavior is similar to a single device detecting an error.
You can have multiple devices that contain the same configuration data in your
system. To support this configuration scheme, all device nCEinputs are tied to GND,
while the nCEOpins are left floating. All other configuration pins (nCONFIG
DATA[0], and CONF_DONE) are connected to every device in the chain.
Configuration signals can require buffering to ensure signal integrity and prevent
, nSTATUS,
DCLK
,
clock skew problems. Ensure that the DCLKand DATAlines are buffered. Devices must
be of the same density and package. All devices start and complete configuration at
the same time.
August 2012 Altera Corporation
Cyclone III Device Handbook
Volume 1
ALTERA [ ALTERA CORPORATION ]
