EP3C120F484C7 Datasheet, PDF (168/274 Pages) Altera Corporation – Cyclone III Device Handbook

9–10
Chapter 9: Configuration, Design Security, and Remote System Upgrades in the Cyclone III Device Family
Configuration Features
Initialization
In Cyclone III device family, the clock source for initialization is either a 10-MHz
(typical) internal oscillator (separate from the AS internal oscillator) or an 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 a
proper initialization. When using the internal oscillator, you do not need 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
from 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, the Cyclone III device family requires a certain amount of clock cycles to
initialize and to enter user mode.
Table 9–5 lists the required clock cycles for proper initialization in Cyclone III device
family.
Table 9–5. Initialization Clock Cycles Required in Cyclone III Device Family
Device
Initialization Clock Cycles
Cyclone III
Cyclone III LS
3,185
3,192
Table 9–6 lists the maximum CLKUSR frequency (f_MAX) for Cyclone III device family.
Table 9–6. Maximum CLKUSR Frequency for Cyclone III Device Family
Device
Cyclone III
Cyclone III LS
f_MAX (MHz)
133
100
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 that 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 from 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
Cyclone III Device Handbook
Volume 1
August 2012 Altera Corporation