EP2C5F256C6N Datasheet, PDF (33/168 Pages) Altera Corporation – Section I. Cyclone II Device Family Data Sheet

Cyclone II Architecture
Global Clock Network
The 16 or 8 global clock networks drive throughout the entire device.
Dedicated clock pins (CLK[]), PLL outputs, the logic array, and
dual-purpose clock (DPCLK[]) pins can also drive the global clock
network.
The global clock network can provide clocks for all resources within the
device, such as IOEs, LEs, memory blocks, and embedded multipliers.
The global clock lines can also be used for control signals, such as clock
enables and synchronous or asynchronous clears fed from the external
pin, or DQS signals for DDR SDRAM or QDRII SRAM interfaces. Internal
logic can also drive the global clock network for internally generated
global clocks and asynchronous clears, clock enables, or other control
signals with large fan-out.
Clock Control Block
There is a clock control block for each global clock network available in
Cyclone II devices. The clock control blocks are arranged on the device
periphery and there are a maximum of 16 clock control blocks available
per Cyclone II device. The larger Cyclone II devices (EP2C15 devices and
larger) have 16 clock control blocks, four on each side of the device. The
smaller Cyclone II devices (EP2C5 and EP2C8 devices) have eight clock
control blocks, four on the left and right sides of the device.
The control block has these functions:
■ Dynamic global clock network clock source selection
■ Dynamic enable/disable of the global clock network
In Cyclone II devices, the dedicated CLK[] pins, PLL counter outputs,
DPCLK[] pins, and internal logic can all feed the clock control block. The
output from the clock control block in turn feeds the corresponding
global clock network.
The following sources can be inputs to a given clock control block:
■ Four clock pins on the same side as the clock control block
■ Three PLL clock outputs from a PLL
■ Four DPCLK pins (including CDPCLK pins) on the same side as the
clock control block
■ Four internally-generated signals
Altera Corporation
February 2007
2–21
Cyclone II Device Handbook, Volume 1