XC4028XL-2HQ304C Xilinx Inc, XC4028XL-2HQ304C Datasheet - Page 14
![no-image](/images/no-image-200.jpg)
XC4028XL-2HQ304C
Manufacturer Part Number
XC4028XL-2HQ304C
Description
IC FPGA C-TEMP 3.3V 2SPD 304HQFP
Manufacturer
Xilinx Inc
Series
XC4000E/Xr
Datasheet
1.XC4005E-4PC84C.pdf
(68 pages)
Specifications of XC4028XL-2HQ304C
Number Of Logic Elements/cells
2432
Number Of Labs/clbs
1024
Total Ram Bits
32768
Number Of I /o
256
Number Of Gates
28000
Voltage - Supply
3 V ~ 3.6 V
Mounting Type
Surface Mount
Operating Temperature
0°C ~ 85°C
Package / Case
304-BFQFP Exposed Pad
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
XC4000E and XC4000X Series Field Programmable Gate Arrays
Fast Carry Logic
Each CLB F and G function generator contains dedicated
arithmetic logic for the fast generation of carry and borrow
signals. This extra output is passed on to the function gen-
erator in the adjacent CLB. The carry chain is independent
of normal routing resources.
Dedicated fast carry logic greatly increases the efficiency
and performance of adders, subtractors, accumulators,
comparators and counters. It also opens the door to many
new applications involving arithmetic operation, where the
previous generations of FPGAs were not fast enough or too
inefficient. High-speed address offset calculations in micro-
processor or graphics systems, and high-speed addition in
digital signal processing are two typical applications.
The two 4-input function generators can be configured as a
2-bit adder with built-in hidden carry that can be expanded
to any length. This dedicated carry circuitry is so fast and
efficient that conventional speed-up methods like carry
generate/propagate are meaningless even at the 16-bit
level, and of marginal benefit at the 32-bit level.
This fast carry logic is one of the more significant features
of the XC4000 Series, speeding up arithmetic and counting
into the 70 MHz range.
The carry chain in XC4000E devices can run either up or
down. At the top and bottom of the columns where there
are no CLBs above or below, the carry is propagated to the
right. (See
high-capacity XC4000X devices, which can potentially
have very long carry chains, the carry chain travels upward
only, as shown in
nect can be used to route a carry signal in the downward
direction.
Figure 13 on page 19
cated fast carry logic. The carry logic in the XC4000X is
similar, except that COUT exits at the top only, and the sig-
nal CINDOWN does not exist. As shown in
carry logic shares operand and control inputs with the func-
tion generators. The carry outputs connect to the function
generators, where they are combined with the operands to
form the sums.
Figure 14 on page 20
for the XC4000E. This diagram shows the contents of the
box labeled “CARRY LOGIC” in
carry logic is very similar, but a multiplexer on the
pass-through carry chain has been eliminated to reduce
delay. Additionally, in the XC4000X the multiplexer on the
G4 path has a memory-programmable 0 input, which per-
mits G4 to directly connect to COUT. G4 thus becomes an
additional high-speed initialization path for carry-in.
The dedicated carry logic is discussed in detail in Xilinx
document XAPP 013: “ Using the Dedicated Carry Logic in
6-18
Figure
Figure
11.) In order to improve speed in the
shows an XC4000E CLB with dedi-
shows the details of the carry logic
12. Additionally, standard intercon-
Product Obsolete or Under Obsolescence
Figure
13. The XC4000X
Figure
13, the
XC4000 .” This discussion also applies to XC4000E
devices, and to XC4000X devices when the minor logic
changes are taken into account.
The fast carry logic can be accessed by placing special
library symbols, or by using Xilinx Relationally Placed Mac-
ros (RPMs) that already include these symbols.
Figure 11: Available XC4000E Carry Propagation
Paths
Figure 12: Available XC4000X Carry Propagation
Paths (dotted lines use general interconnect)
X6610
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
May 14, 1999 (Version 1.6)
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
CLB
X6687
R