2–2
Chapter 2: Logic Elements and Logic Array Blocks in Cyclone IV Devices
Logic Elements
November 2009
Altera Corporation
shows the LEs for Cyclone IV devices.
LE Features
You can configure the programmable register of each LE for D, T, JK, or SR flipflop
operation. Each register has data, clock, clock enable, and clear inputs. Signals that
use the global clock network, general-purpose I/O pins, or any internal logic can
drive the clock and clear control signals of the register. Either general-purpose I/O
pins or the internal logic can drive the clock enable. For combinational functions, the
LUT output bypasses the register and drives directly to the LE outputs.
Each LE has three outputs that drive the local, row, and column routing resources. The
LUT or register output independently drives these three outputs. Two LE outputs
drive the column or row and direct link routing connections, while one LE drives the
local interconnect resources. This allows the LUT to drive one output while the
register drives another output. This feature, called register packing, improves device
utilization because the device can use the register and the LUT for unrelated
functions. The LAB-wide synchronous load control signal is not available when using
register packing. For more information about the synchronous load control signal,
refer to
“LAB Control Signals” on page 2–6
The register feedback mode allows the register output to feed back into the LUT of the
same LE to ensure that the register is packed with its own fan-out LUT, providing
another mechanism for improved fitting. The LE can also drive out registered and
unregistered versions of the LUT output.
Figure 2–1. Cyclone IV Device LEs
Row, Col
u
mn,
And Direct Link
Ro
u
ting
data 1
data 2
data 3
data 4
labclr1
labclr2
Chip-
W
ide
Reset
(DEV_CLRn)
labclk1
labclk2
labclkena1
labclkena2
LE Carry-In
LAB-
W
ide
Synchrono
u
s
Load
LAB-
W
ide
Synchrono
u
s
Clear
Row, Col
u
mn,
And Direct Link
Ro
u
ting
Local
Ro
u
ting
Register Chain
O
u
tp
u
t
Register Bypass
Programmable
Register
Register Chain
Ro
u
ting from
previo
u
s LE
LE Carry-O
u
t
Register Feedback
Synchrono
u
s
Load and
Clear Logic
Carry
Chain
Look-Up Table
(LUT)
Asynchrono
u
s
Clear Logic
Clock &
Clock Enable
Select
D
Q
ENA
CLRN
Summary of Contents for Cyclone IV
Page 10: ...x Chapter Revision Dates Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Page 14: ...I 2 Section I Device Core Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Page 274: ...vi Contents Cyclone IV Device Handbook February 2015 Altera Corporation Volume 2...
Page 440: ...iv Contents Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
Page 442: ...vi Chapter Revision Dates Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
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