Chapter 8: Configuration and Remote System Upgrades in Cyclone IV Devices
8–7
Configuration
May 2013
Altera Corporation
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
s), 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
s).
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-k
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.
Summary of Contents for Cyclone IV
Page 10: ...x Chapter Revision Dates Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Page 14: ...I 2 Section I Device Core Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Page 274: ...vi Contents Cyclone IV Device Handbook February 2015 Altera Corporation Volume 2...
Page 440: ...iv Contents Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
Page 442: ...vi Chapter Revision Dates Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
Page 446: ......