EP2S90F1020C5 Datasheet, PDF (617/768 Pages) Altera Corporation – Stratix II Device Handbook, Volume 1

Configuring Stratix II and Stratix II GX Devices
You can cascade several EPC2 devices to configure multiple Stratix II or
Stratix II GX devices. The first configuration device in the chain is the
master configuration device, while the subsequent devices are the slave
devices. The master configuration device sends DCLK to the Stratix II or
Stratix II GX devices and to the slave configuration devices. The first EPC
device’s nCS pin is connected to the CONF_DONE pins of the devices,
while its nCASC pin is connected to nCS of the next configuration device
in the chain. The last device’s nCS input comes from the previous device,
while its nCASC pin is left floating. When all data from the first
configuration device is sent, it drives nCASC low, which in turn drives
nCS on the next configuration device. A configuration device requires
less than one clock cycle to activate a subsequent configuration device, so
the data stream is uninterrupted.
1 Enhanced configuration devices cannot be cascaded.
Because all nSTATUS and CONF_DONE pins are tied together, if any device
detects an error, the master configuration device stops configuration for
the entire chain and the entire chain must be reconfigured. For example,
if the master configuration device does not detect CONF_DONE going high
at the end of configuration, it resets the entire chain by pulling its OE pin
low. This low signal drives the OE pin low on the slave configuration
device(s) and drives nSTATUS low on all devices, causing them to enter a
reset state. This behavior is similar to the device detecting an error in the
configuration data.
Altera Corporation
January 2008
7–65
Stratix II Device Handbook, Volume 2