![](http://datasheet.mmic.net.cn/Xilinx-Inc/XC3S1600E-5FGG484C_datasheet_99960/XC3S1600E-5FGG484C_61.png)
Spartan-3E FPGA Family: Functional Description
DS312 (v4.1) July 19, 2013
Product Specification
61
The connections for the bottom-edge BUFGMUX elements
are similar to the top-edge connections (see
Figure 46).
On the left and right edges, only two clock inputs feed each
pair of BUFGMUX elements.
Quadrant Clock Routing
The clock routing within the FPGA is quadrant-based, as
shown in
Figure 45. Each clock quadrant supports eight
total clock signals, labeled ‘A’ through ‘H’ in
Table 41 and
Figure 47. The clock source for an individual clock line
originates either from a global BUFGMUX element along
the top and bottom edges or from a BUFGMUX element
along the associated edge, as shown in
Figure 47. The
clock lines feed the synchronous resource elements (CLBs,
IOBs, block RAM, multipliers, and DCMs) within the
quadrant.
The four quadrants of the device are:
Top Right (TR)
Bottom Right (BR)
Bottom Left (BL)
Top Left (TL)
Note that the quadrant clock notation (TR, BR, BL, TL) is
separate from that used for similar IOB placement
constraints.
To estimate the quadrant location for a particular I/O, see
exact quadrant locations, use the floorplanning tool. In the
QFP packages (VQ100, TQ144 and PQ208) the quadrant
borders fall in the middle of each side of the package, at a
GND pin. The clock inputs fall on the quadrant boundaries,
In a few cases, a dedicated input is physically in one
quadrant of the device but connects to a different clock
quadrant:
FT256, H16 is in clock quadrant BR
FG320, K2 is in clock quadrant BL
FG400, L8 is in clock quadrant TL and the I/O at N11 is
in clock quadrant BL
FG484, M2 is in clock quadrant TL and L15 is in clock
quadrant BR
X-Ref Target - Figure 46
Figure 46: Clock Switch Matrix to BUFGMUX Pair Connectivity
BUFGMUX
LHCLK or
RHCLK input
Double Line
DCM output*
Left-/Right-Half BUFGMUX
CLK Switch
Matrix
S
O
S
I1
I0
I1
I0
BUFGMUX
Top/Bottom (Global) BUFGMUX
CLK Switch
Matrix
S
O
S
I1
I0
I1
I0
1st GCLK pin
2nd GCLK pin
1st DCM output
2nd DCM output
Double Line
DS312-2_16_110706
0
1
0
1
0
1
0
1
*(XC3S1200E and
XC3S1600E only)
Table 42: QFP Package Clock Quadrant Locations
Clock Pins
Quadrant
GCLK[3:0]
BR
GCLK[7:4]
TR
GCLK[11:8]
TL
GCLK[15:12]
BL
RHCLK[3:0]
BR
RHCLK[7:4]
TR
LHCLK[3:0]
TL
LHCLK[7:4]
BL