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先3q楼上的，你真是一个好人 但是它的时钟输入那是干什么的？是不是我们也可以通过这几个引脚来输入控制时钟（在I/O引脚不够时）？ 英文如下：Clocking
Each I/O and buried macrocell has access to four synchronous
clocks (CLK0, CLK1, CLK2 and CLK3) as well as an
asynchronous product term clock PTCLK. Each input
macrocell has access to all four synchronous clocks.
Dedicated Inputs/Clocks
Five pins on each member of the Ultra37000 family are designated
as input-only. There are two types of dedicated inputs
on Ultra37000 devices: input pins and input/clock pins.
Figure 3 illustrates the architecture for input pins. Four input
options are available for the user: combinatorial, registered,
double-registered, or latched. If a registered or latched option
is selected, any one of the input clocks can be selected for
control.
Figure 4 illustrates the architecture for the input/clock pins.
Like the input pins, input/clock pins can be combinatorial,
registered, double-registered, or latched. In addition, these
pins feed the clocking structures throughout the device. The
clock path at the input has user-configurable polarity.
Product Term Clocking
In addition to the four synchronous clocks, the Ultra37000
family also has a product term clock for asynchronous
clocking. Each logic block has an independent product term
clock which is available to all 16 macrocells. Each product term
clock also supports user configurable polarity selection. | 
发表于 2007-6-14 17:52:00
楼主