XC3S250E Xilinx, Inc., XC3S250E Datasheet - Page 59

• Manufacturer Part Number: XC3S250E
• Description: Spartan-3E FPGA Family
• Manufacturer: Xilinx, Inc.

Functional Description
The outputs of the top or bottom BUFGMUX elements con-
nect to two vertical spines, each comprising four vertical
clock lines as shown in
these clock signals connect to the eight-line horizontal clock
spine.
Outputs of the left and right BUFGMUX elements are routed
onto the left or right horizontal spines, each comprising
eight horizontal clock lines.
Each of the eight clock signals in a clock quadrant derives
either from a global clock signal or a half clock signal. In
other words, there are up to 24 total potential clock inputs to
the FPGA, eight of which can connect to clocked elements
52
Figure 44: Clock Sources for the Eight Clock Lines within a Clock Quadrant
a. Left (TL and BL Quadrants) Half of Die
BUFGMUX Output
X0Y2 (Left Half)
X0Y3 (Left Half)
X0Y4 (Left Half)
X0Y5 (Left Half)
X0Y6 (Left Half)
X0Y7 (Left Half)
X0Y8 (Left Half)
X0Y9 (Left Half)
X2Y11 (Global)
X2Y10 (Global)
X1Y11 (Global)
X1Y10 (Global)
X2Y1 (Global)
X2Y0 (Global)
X1Y1 (Global)
X1Y0 (Global)
Figure
42. At the center of the die,
Clock Line
www.xilinx.com
A
B
C
D
E
F
G
H
b. Right (TR and BR Quadrants) Half of Die
X3Y2 (Right Half)
X3Y3 (Right Half)
X3Y4 (Right Half)
X3Y5 (Right Half)
X3Y6 (Right Half)
X3Y7 (Right Half)
X3Y8 (Right Half)
X3Y9 (Right Half)
in a single clock quadrant.
lines in each quadrant are selected from associated BUFG-
MUX sources. For example, if quadrant clock ‘A’ in the bot-
tom left (BL) quadrant originates from BUFGMUX_X2Y1,
then the clock signal from BUFGMUX_X0Y2 is unavailable
in the bottom left quadrant. However, the top left (TL) quad-
rant clock ‘A’ can still solely use the output from either
BUFGMUX_X2Y1 or BUFGMUX_X0Y2 as the source.
To minimize the dynamic power dissipation of the clock net-
work, the Xilinx development software automatically dis-
ables all clock segments not in use.
BUFGMUX Output
X2Y11 (Global)
X2Y10 (Global)
X1Y11 (Global)
X1Y10 (Global)
X2Y1 (Global)
X2Y0 (Global)
X1Y1 (Global)
X1Y0 (Global)
DS312-2_17_030105
Figure 44
Advance Product Specification
Clock Line
DS312-2 (v1.1) March 21, 2005
A
B
C
D
E
F
G
H
shows how the clock
R