EP4CE30F29C7N Datasheet, PDF (171/488 Pages) Altera Corporation – Cyclone IV Device Handbook, Volume 1

Chapter 8: Configuration and Remote System Upgrades in Cyclone IV Devices
8–7
Configuration
You can begin reconfiguration by pulling the nCONFIG pin low. The nCONFIG pin must
be low for at least 500 ns. When nCONFIG is pulled low, the Cyclone IV device is reset.
The Cyclone IV device also pulls nSTATUS and CONF_DONE low and all I/O pins are
tri-stated. When nCONFIG returns to a logic-high level and nSTATUS is released by the
Cyclone IV device, reconfiguration begins.
Configuration Error
If an error occurs during configuration, Cyclone IV devices assert the nSTATUS signal
low, indicating a data frame error and the CONF_DONE signal stays low. If the
Auto-restart configuration after error option (available in the Quartus II software in
the General tab of the Device and Pin Options dialog box) is turned on, the
Cyclone IV device releases nSTATUS after a reset time-out period (a maximum of
230 μs), and retries configuration. If this option is turned off, the system must monitor
nSTATUS for errors and then pulse nCONFIG low for at least 500 ns to restart
configuration.
Initialization
In Cyclone IV devices, the initialization clock source is either the internal oscillator or
the optional CLKUSR pin. By default, the internal oscillator is the clock source for
initialization. If you use the internal oscillator, the device provides itself with enough
clock cycles for proper initialization. When using the internal oscillator, you do not
have to send additional clock cycles from an external source to the CLKUSR pin during
the initialization stage. Additionally, you can use the CLKUSR pin as a user I/O pin.
You also have the flexibility to synchronize initialization of multiple devices or to
delay initialization with the CLKUSR option. The CLKUSR pin allows you to control
when your device enters user mode for an indefinite amount of time. You can turn on
the Enable user-supplied start-up clock (CLKUSR) option in the Quartus II software
in the General tab of the Device and Pin Options dialog box. When you turn on the
Enable user supplied start-up clock option (CLKUSR) option, the CLKUSR pin is the
initialization clock source. Supplying a clock on the CLKUSR pin does not affect the
configuration process. After the configuration data is accepted and CONF_DONE goes
high, Cyclone IV devices require 3,192 clock cycles to initialize properly and enter
user mode.
1 If you use the optional CLKUSR pin and the nCONFIG pin is pulled low to restart
configuration during device initialization, ensure that the CLKUSR pin continues to
toggle when nSTATUS is low (a maximum of 230 μs).
User Mode
An optional INIT_DONE pin is available, which signals the end of initialization and the
start of user mode with a low-to-high transition. The Enable INIT_DONE Output
option is available in the Quartus II software in the General tab of the Device and Pin
Options dialog box. If you use the INIT_DONE pin, it is high due to an external 10-kΩ
pull-up resistor when nCONFIG is low and during the beginning of configuration. After
the option bit to enable INIT_DONE is programmed into the device (during the first
frame of configuration data), the INIT_DONE pin goes low. When initialization is
complete, the INIT_DONE pin is released and pulled high. This low-to-high transition
signals that the device has entered user mode. In user mode, the user I/O pins
function as assigned in your design and no longer have weak pull-up resistors.
May 2013 Altera Corporation
Cyclone IV Device Handbook,
Volume 1