Virtex-E 1.8 V Extended Memory Field Programmable Gate Arrays
Module 2 of 4
DS025-2 (v3.0) March 21, 2014
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Table 5 shows the depth and width aspect ratios for the
block SelectRAM. The Virtex-E block SelectRAM also
includes dedicated routing to provide an efficient interface
with both CLBs and other block SelectRAM modules. Refer
to XAPP130 for block SelectRAM timing waveforms.
Programmable Routing Matrix
It is the longest delay path that limits the speed of any
worst-case design. Consequently, the Virtex-E routing
architecture and its place-and-route software were defined
in a joint optimization process. This joint optimization mini-
mizes long-path delays, and consequently, yields the best
system performance.
The joint optimization also reduces design compilation
times because the architecture is software-friendly. Design
cycles are correspondingly reduced due to shorter design
iteration times.
Local Routing
The VersaBlock, shown in
Figure 7, provides local routing
resources with the following types of connections:
Interconnections among the LUTs, flip-flops, and GRM
Internal CLB feedback paths that provide high-speed
connections to LUTs within the same CLB, chaining
them together with minimal routing delay
Direct paths that provide high-speed connections
between horizontally adjacent CLBs, eliminating the
delay of the GRM
.
General Purpose Routing
Most Virtex-E signals are routed on the general purpose
routing, and consequently, the majority of interconnect
resources are associated with this level of the routing hier-
archy. The general routing resources are located in horizon-
tal and vertical routing channels associated with the CLB
rows and columns. The general-purpose routing resources
are listed below.
Adjacent to each CLB is a General Routing Matrix
(GRM). The GRM is the switch matrix through which
horizontal and vertical routing resources connect, and
is also the means by which the CLB gains access to
the general purpose routing.
24 single-length lines route GRM signals to adjacent
GRMs in each of the four directions.
72 buffered Hex lines route GRM signals to another
GRMs six-blocks away in each one of the four
directions. Organized in a staggered pattern, Hex lines
are driven only at their endpoints. Hex-line signals can
be accessed either at the endpoints or at the midpoint
(three blocks from the source). One third of the Hex
lines are bidirectional, while the remaining ones are
uni-directional.
12 Longlines are buffered, bidirectional wires that
distribute signals across the device quickly and
efficiently. Vertical Longlines span the full height of the
device, and horizontal ones span the full width of the
device.
I/O Routing
Virtex-E devices have additional routing resources around
their periphery that form an interface between the CLB array
and the IOBs. This additional routing, called the VersaRing,
facilitates pin-swapping and pin-locking, such that logic
redesigns can adapt to existing PCB layouts. Time-to-mar-
ket is reduced, since PCBs and other system components
can be manufactured while the logic design is still in prog-
ress.
Figure 6: Dual-Port Block SelectRAM
Table 5:
Block SelectRAM Port Aspect Ratios
Width
Depth
ADDR Bus
Data Bus
1
4096
ADDR<11:0>
DATA<0>
2
2048
ADDR<10:0>
DATA<1:0>
4
1024
ADDR<9:0>
DATA<3:0>
8
512
ADDR<8:0>
DATA<7:0>
16
256
ADDR<7:0>
DATA<15:0>
WEB
ENB
RSTB
CLKB
ADDRB[#:0]
DIB[#:0]
WEA
ENA
RSTA
CLKA
ADDRA[#:0]
DIA[#:0]
DOA[#:0]
DOB[#:0]
RAMB4_S#_S#
ds022_06_121699
Figure 7: Virtex-E Local Routing
XCVE_ds_007
CLB
GRM
To
Adjacent
GRM
To Adjacent
GRM
Direct
Connection
To Adjacent
CLB
To Adjacent
GRM
To Adjacent
GRM
Direct Connection
To Adjacent
CLB