EP3C55F780I7 Datasheet, PDF (167/274 Pages) Altera Corporation – This section provides a complete overview of all features relating to the Cyclone III device family

Chapter 9: Configuration, Design Security, and Remote System Upgrades in the Cyclone III Device Family
9–9
Configuration Features
When the device exits POR, all user I/O pins continue to tri-state. The user I/O pins
and dual-purpose I/O pins have weak pull-up resistors that are always enabled (after
POR) before and during configuration. After POR, the Cyclone III device family
releases nSTATUS, which is pulled high by an external 10-k pull-up resistor and
enters configuration mode.
When nCONFIG goes high, the device exits reset and releases the open-drain nSTATUS
pin, which is then pulled high by an external 10-kpull-up resistor. After nSTATUS is
released, the device is ready to receive configuration data and the configuration stage
begins.
Cyclone III LS devices are accessible by limited JTAG instructions after POR. For more
information about enabling full JTAG instructions access, refer to “JTAG Instructions”
on page 9–60.
f For more information about the value of weak pull-up resistors on the I/O pins that
are on before and during configuration, refer to the Cyclone III Device Data Sheet and
Cyclone III LS Device Data Sheet chapters.
Configuration
Configuration data is latched into the Cyclone III device family at each DCLK cycle.
However, the width of the data bus and the configuration time taken for each scheme
are different. After the device receives all the configuration data, the device releases
the open-drain CONF_DONE pin, which is pulled high by an external 10-kpull-up
resistor. A low-to-high transition on the CONF_DONE pin indicates that configuration is
complete and initialization of the device can begin. The CONF_DONE pin must have an
external 10-k pull-up resistor for the device to initialize.
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 III device family is
reset. The Cyclone III device family 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 III device family, reconfiguration begins.
Configuration Error
If an error occurs during configuration, the Cyclone III device family asserts 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 from the General tab of the Device and Pin Options dialog box) is turned
on, the Cyclone III device family 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.
August 2012 Altera Corporation
Cyclone III Device Handbook
Volume 1