Cyclone FPGA Family Data Sheet
Preliminary Information
Operating Modes
The Cyclone architecture uses SRAM configuration elements that require
configuration data to be loaded each time the circuit powers up. The
process of physically loading the SRAM data into the device is called
configuration. During initialization, which occurs immediately after
configuration, the device resets registers, enables I/O pins, and begins to
operate as a logic device. Together, the configuration and initialization
processes are called command mode. Normal device operation is called
user mode.
SRAM configuration elements allow Cyclone devices to be reconfigured
in-circuit by loading new configuration data into the device. With real-
time reconfiguration, the device is forced into command mode with a
device pin. The configuration process loads different configuration data,
reinitializes the device, and resumes user-mode operation. Designers can
perform in-field upgrades by distributing new configuration files either
within the system or remotely.
A built-in weak pull-up resistor pulls all user I/O pins to VCCIO before
and during device configuration.
The configuration pins support 1.5-V/1.8-V or 2.5-V/3.3-V I/O standards.
The voltage level of the configuration output pins is determined by the
VCCIO of the bank where the pins reside. The bank VCCIO selects whether
the configuration inputs are 1.5-V, 1.8-V, 2.5-V, or 3.3-V compatible.
Configuration Schemes
Designers can load the configuration data for a Cyclone device with one
of three configuration schemes (see Table 22), chosen on the basis of the
target application. Designers can use a configuration device, intelligent
controller, or the JTAG port to configure a Cyclone device. A low-cost
configuration device can automatically configure a Cyclone device at
system power-up.
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Altera Corporation
ALTERA [ ALTERA CORPORATION ]
