EP2C20F256C8N Datasheet, PDF (46/470 Pages) Altera Corporation – Cyclone II Device Handbook, Volume 1

Global Clock Network & Phase-Locked Loops
Dedicated Clock Pins
Larger Cyclone II devices (EP2C15 and larger devices) have 16 dedicated
clock pins (CLK[15..0], four pins on each side of the device). Smaller
Cyclone II devices (EP2C5 and EP2C8 devices) have eight dedicated clock
pins (CLK[7..0], four pins on left and right sides of the device). These
CLK pins drive the global clock network (GCLK), as shown in
Figures 2–11 and 2–12.
If the dedicated clock pins are not used to feed the global clock networks,
they can be used as general-purpose input pins to feed the logic array
using the MultiTrack interconnect. However, if they are used as general-
purpose input pins, they do not have support for an I/O register and
must use LE-based registers in place of an I/O register.
Dual-Purpose Clock Pins
Cyclone II devices have either 20 dual-purpose clock pins,
DPCLK[19..0] or 8 dual-purpose clock pins, DPCLK[7..0]. In the
larger Cyclone II devices (EP2C15 devices and higher), there are
20 DPCLK pins; four on the left and right sides and six on the top and
bottom of the device. The corner CDPCLK pins are first multiplexed before
they drive into the clock control block. Since the signals pass through a
multiplexer before feeding the clock control block, these signals incur
more delay to the clock control block than other DPCLK pins that directly
feed the clock control block. In the smaller Cyclone II devices (EP2C5 and
EP2C8 devices), there are eight DPCLK pins; two on each side of the device
(see Figures 2–11 and 2–12).
A programmable delay chain is available from the DPCLK pin to its fan-
out destinations. To set the propagation delay from the DPCLK pin to its
fan-out destinations, use the Input Delay from Dual-Purpose Clock Pin
to Fan-Out Destinations assignment in the Quartus II software.
These dual-purpose pins can connect to the global clock network for
high-fanout control signals such as clocks, asynchronous clears, presets,
and clock enables, or protocol control signals such as TRDY and IRDY for
PCI, or DQS signals for external memory interfaces.
2–20
Cyclone II Device Handbook, Volume 1
Altera Corporation
February 2007