Virtex-E 1.8 V Extended Memory Field Programmable Gate Arrays
DS025-2 (v3.0) March 21, 2014
Module 2 of 4
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bined to create a 16 x 2-bit or 32 x 1-bit synchronous RAM,
or a 16 x 1-bit dual-port synchronous RAM.
The Virtex-E LUT can also provide a 16-bit shift register that
is ideal for capturing high-speed or burst-mode data. This
mode can also be used to store data in applications such as
Digital Signal Processing.
Storage Elements
The storage elements in the Virtex-E slice can be config-
ured either as edge-triggered D-type flip-flops or as
level-sensitive latches. The D inputs can be driven either by
the function generators within the slice or directly from slice
inputs, bypassing the function generators.
In addition to Clock and Clock Enable signals, each Slice
has synchronous set and reset signals (SR and BY). SR
forces a storage element into the initialization state speci-
fied for it in the configuration. BY forces it into the opposite
state. Alternatively, these signals can be configured to oper-
ate asynchronously. All of the control signals are indepen-
dently invertible, and are shared by the two flip-flops within
the slice.
Additional Logic
The F5 multiplexer in each slice combines the function gen-
erator outputs. This combination provides either a function
generator that can implement any 5-input function, a 4:1
multiplexer, or selected functions of up to nine inputs.
Similarly, the F6 multiplexer combines the outputs of all four
function generators in the CLB by selecting one of the
F5-multiplexer outputs. This permits the implementation of
any 6-input function, an 8:1 multiplexer, or selected func-
tions of up to 19 inputs.
Each CLB has four direct feedthrough paths, two per slice.
These paths provide extra data input lines or additional local
routing that does not consume logic resources.
Arithmetic Logic
Dedicated carry logic provides fast arithmetic carry capabil-
ity for high-speed arithmetic functions. The Virtex-E CLB
supports two separate carry chains, one per Slice. The
height of the carry chains is two bits per CLB.
The arithmetic logic includes an XOR gate that allows a
2-bit full adder to be implemented within a slice. In addition,
a dedicated AND gate improves the efficiency of multiplier
implementation.
The dedicated carry path can also be used to cascade func-
tion generators for implementing wide logic functions.
BUFTs
Each Virtex-E CLB contains two 3-state drivers (BUFTs)
page 7. Each Virtex-E BUFT has an independent 3-state
control pin and an independent input pin.
Block SelectRAM+ Memory
Virtex-E FPGAs incorporate large block SelectRAM memo-
ries. These complement the Distributed SelectRAM memo-
ries that provide shallow RAM structures implemented in
CLBs.
Block SelectRAM memory blocks are organized in columns,
starting at the left (column 0) and right outside edges and
inserted every four CLB columns (see notes for smaller
devices). Each memory block is four CLBs high, and each
memory column extends the full height of the chip, immedi-
ately adjacent (to the right, except for column 0) of the CLB
column locations indicated in
Table 3.
Table 4 shows the amount of block SelectRAM memory that
is available in each Virtex-E device.
Each block SelectRAM cell, as illustrated in
Figure 6, is a
fully synchronous dual-ported (True Dual Port) 4096-bit
RAM with independent control signals for each port. The
data widths of the two ports can be configured indepen-
dently, providing built-in bus-width conversion.
Table 3:
CLB/Block RAM Column Locations
Virtex-E Device
0
4
8
12
16
20
24
28
32
36
40
444852566064
68
72
76
80
84
XCV405E
√ √ √ √
√
√√√√√
XCV812E
√ √ √ √
√
√√√√√√√√√√
Table 4:
Virtex-E Block SelectRAM Amounts
Virtex-E Device
# of Blocks
Block SelectRAM Bits
XCV405E
140
573,440
XCV812E
280
1,146,880