ep1m120 Altera Corporation, ep1m120 Datasheet - Page 19

• Manufacturer Part Number: ep1m120
• Description: Programmable Logic Device Family
• Manufacturer: Altera Corporation

Altera Corporation
Each LE has two outputs that drive the local, row, and column routing
resources. Each output can be driven independently by the LUT’s or
register’s output. For example, the LUT can drive one output, while the
register drives the other output. This feature, called register packing,
improves device utilization because the register and the LUT can be used
for unrelated functions. The LE can also drive out registered and
unregistered versions of the LUT output.
LE Operating Modes
The Mercury LE can operate in one of the following modes:
Each operating mode uses LE resources differently. In each operating
mode, eight available inputs to the LE—the four data inputs from the LAB
local interconnect; carry-in0, carry-in1 from the previous LE; the
LAB carry-in from the previous carry-chain generation; and the FastLUT
Connection input from the previous LE—are directed to different
destinations to implement the desired logic function. LAB-wide signals
provide clock, asynchronous clear, asynchronous preset, asynchronous
load, synchronous clear, synchronous load, and clock enable control for
the register. These LAB-wide signals are available in all normal and
arithmetic LE modes.
The Quartus II software, in conjunction with parameterized functions
such as LPM and DesignWare functions, automatically chooses the
appropriate mode for common functions, such as counters, adders, and
multipliers. If required, the designer can also create special-purpose
functions that specify which LE operating mode to use for optimal
performance.
Normal Mode
The normal mode is suitable for general logic applications and
combinatorial functions. In normal mode, four data inputs from the LAB
local interconnect and a single carry-in are inputs to a four-input LUT. The
Quartus II Compiler automatically selects the carry-in or the data3 signal
as one of the inputs to the LUT. The LUT (combinatorial) output can be
driven to the FastLUT connection to the next LE in the LAB. LEs in normal
mode support packed registers.
Normal
Arithmetic
Multiplier
Mercury Programmable Logic Device Family Data Sheet
Figure 8
shows an LE in normal mode.
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