R
Spartan and Spartan-XL FPGA Families Data Sheet
Six Pass Transistors Per
Switch Matrix Interconnect Point
DS060_10_081100
Figure 10: Programmable Switch Matrix
I/O Routing
Double-Length Lines
The double-length lines consist of a grid of metal segments,
each twice as long as the single-length lines: they run past
two CLBs before entering a PSM. Double-length lines are
grouped in pairs with the PSMs staggered, so that each line
goes through a PSM at every other row or column of CLBs
(see Figure 8).
Spartan/XL devices have additional routing around the IOB
ring. This routing is called a VersaRing. The VersaRing facil-
itates pin-swapping and redesign without affecting board
layout. Included are eight double-length lines, and four lon-
glines.
Global Nets and Buffers
There are four vertical and four horizontal double-length
lines associated with each CLB. These lines provide faster
signal routing over intermediate distances, while retaining
routing flexibility.
The Spartan/XL devices have dedicated global networks.
These networks are designed to distribute clocks and other
high fanout control signals throughout the devices with min-
imal skew.
Longlines
Four vertical longlines in each CLB column are driven exclu-
sively by special global buffers. These longlines are in addi-
tion to the vertical longlines used for standard interconnect.
In the 5V Spartan devices, the four global lines can be
driven by either of two types of global buffers; Primary Glo-
bal buffers (BUFGP) or Secondary Global buffers (BUFGS).
Each of these lines can be accessed by one particular Pri-
mary Global buffer, or by any of the Secondary Global buff-
ers, as shown in Figure 11. In the 3V Spartan-XL devices,
the four global lines can be driven by any of the eight Global
Low-Skew Buffers (BUFGLS). The clock pins of every CLB
and IOB can also be sourced from local interconnect.
Longlines form a grid of metal interconnect segments that
run the entire length or width of the array. Longlines are
intended for high fan-out, time-critical signal nets, or nets
that are distributed over long distances.
Each Spartan/XL device longline has a programmable split-
ter switch at its center. This switch can separate the line into
two independent routing channels, each running half the
width or height of the array.
Routing connectivity of the longlines is shown in Figure 8.
The longlines also interface to some 3-state buffers which is
described later in 3-State Long Line Drivers, page 19.
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DS060 (v1.8) June 26, 2008
Product Specification
XILINX [ XILINX, INC ]
