EP2C8T144I8N Datasheet, PDF (399/470 Pages) Altera Corporation – Cyclone II Device Handbook, Volume 1

Configuring Cyclone II Devices
devices and to the slave configuration devices. Connect the first
configuration device’s nCS pin to all the Cyclone II device’s CONF_DONE
pins, and connect the nCASC pin to the nCS pin of the next configuration
device in the chain. Leave the nCASC pin of the last configuration device
floating. When the master configuration device sends all the data to the
Cyclone II device, the configuration device transitions the nCASC pin
low, which drives nCS on the next configuration device. Because a
configuration device requires less than one clock cycle to activate a
subsequent configuration device, the data stream is uninterrupted.
1
Enhanced configuration devices (EPC16, EPC8, and EPC4
devices) cannot be cascaded.
Since all nSTATUS and CONF_DONE pins are connected, 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 the Cyclone II device’s
CONF_DONE pin transitioning high at the end of configuration, it resets
the entire chain by transitioning its OE pin low. This low signal drives the
OE pin low on the slave configuration device(s) and drives nSTATUS low
on all Cyclone II devices, causing them to enter a reset state. This
behavior is similar to the FPGA detecting an error in the configuration
data.
Figure 13–17 shows how to configure multiple devices using cascaded
EPC2 or EPC1 devices.
Altera Corporation
February 2007
13–45
Cyclone II Device Handbook, Volume 1