R
Spartan and Spartan-XL Families Field Programmable Gate Arrays
8 Singles
PSM
PSM
PSM
2 Doubles
3 Longs
CLB
CLB
3 Longs
2 Doubles
PSM
PSM
PSM
2 Doubles
3 Longs 8 Singles 3 Longs
2 Doubles
DS060_09_041901
Figure 8: Spartan/XL CLB Routing Channels and Interface Block Diagram
CLB Interface
Programmable Switch Matrices
A block diagram of the CLB interface signals is shown in
Figure 9. The input signals to the CLB are distributed evenly
on all four sides providing maximum routing flexibility. In
general, the entire architecture is symmetrical and regular.
It is well suited to established placement and routing algo-
rithms. Inputs, outputs, and function generators can freely
swap positions within a CLB to avoid routing congestion
during the placement and routing operation. The exceptions
are the clock (K) input and CIN/COUT signals. The K input
is routed to dedicated global vertical lines as well as four
single-length lines and is on the left side of the CLB. The
CIN/COUT signals are routed through dedicated intercon-
nects which do not interfere with the general routing struc-
ture. The output signals from the CLB are available to drive
both vertical and horizontal channels.
The horizontal and vertical single- and double-length lines
intersect at a box called a programmable switch matrix
(PSM). Each PSM consists of programmable pass transis-
tors used to establish connections between the lines (see
Figure 10).
For example, a single-length signal entering on the right
side of the switch matrix can be routed to a single-length
line on the top, left, or bottom sides, or any combination
thereof, if multiple branches are required. Similarly, a dou-
ble-length signal can be routed to a double-length line on
any or all of the other three edges of the programmable
switch matrix.
Single-Length Lines
Single-length lines provide the greatest interconnect flexibil-
ity and offer fast routing between adjacent blocks. There are
eight vertical and eight horizontal single-length lines associ-
ated with each CLB. These lines connect the switching
matrices that are located in every row and column of CLBs.
Single-length lines are connected by way of the program-
mable switch matrices, as shown in Figure 10. Routing con-
nectivity is shown in Figure 8.
CIN
COUT
G1
Y
G3
C3
F3
Single-length lines incur a delay whenever they go through
a PSM. Therefore, they are not suitable for routing signals
for long distances. They are normally used to conduct sig-
nals within a localized area and to provide the branching for
nets with fanout greater than one.
C1
K
CLB
F1
X
Rev 1.1
DS060_08_081100
Figure 9: CLB Interconnect Signals
DS060 (v1.6) September 19, 2001
Product Specification
www.xilinx.com
1-800-255-7778
11
XILINX [ XILINX, INC ]
