Device Configuration Pins
Table 13–11. Dedicated Configuration Pins on the Cyclone II Device (Part 3 of 5)
User Configuration
Pin Name
Pin Type
Description
Mode
Scheme
N/A
All
Bidirectional
open-drain
This pin is a status output and input.
CONF_DONE
The target Cyclone II device drives the CONF_DONE
pin low before and during configuration. Once the
Cyclone II device receives all the configuration data
without error and the initialization cycle starts, it
releases CONF_DONE. Driving CONF_DONElow
during user mode does not affect the configured
device. Do not drive CONF_DONElow before the
device enters user mode.
After the Cyclone II device receives all the data, the
CONF_DONEpin transitions high, and the device
initializes and enters user mode. The CONF_DONE
pin must have an external 10-kΩ pull-up resistor in
order for the device to initialize.
Driving CONF_DONElow after configuration and
initialization does not affect the configured device.
The enhanced configuration devices’ and EPC2
devices’ OEand nCSpins are connected to the
Cyclone II device’s nSTATUSand CONF_DONEpins,
respectively, and have optional internal
programmable pull-up resistors. If internal pull-up
resistors on the enhanced configuration device are
used, external 10-kΩ pull-up resistors should not be
used on these pins. When using EPC2 devices, you
should only use external 10-kΩ pull-up resistors.
The input buffer on this pin supports hysteresis using
Schmitt trigger circuitry.
N/A
All
Input
nCE
This pin is an active-low chip enable. The nCEpin
activates the device with a low signal to allow
configuration. The nCEpin must be held low during
configuration, initialization, and user mode. In single
device configuration, it should be tied low. In multiple
device configuration, nCEof the first device is tied low
while its nCEOpin is connected to nCEof the next
device in the chain.
The nCEpin must also be held low for successful
JTAG programming of the FPGA.
The input buffer on this pin supports hysteresis using
Schmitt trigger circuitry.
13–66
Altera Corporation
February 2007
Cyclone II Device Handbook, Volume 1
ALTERA [ ALTERA CORPORATION ]
