EPF8452ATC100-4N Datasheet, PDF (7/62 Pages) Altera Corporation – Programmable Logic Device Family

FLEX 8000 Programmable Logic Device Family Data Sheet
Each LAB provides four control signals that can be used in all eight LEs.
Two of these signals can be used as clocks, and the other two for
clear/preset control. The LAB control signals can be driven directly from
a dedicated input pin, an I/O pin, or any internal signal via the LAB local
interconnect. The dedicated inputs are typically used for global clock,
clear, or preset signals because they provide synchronous control with
very low skew across the device. FLEX 8000 devices support up to four
individual global clock, clear, or preset control signals. If logic is required
on a control signal, it can be generated in one or more LEs in any LAB and
driven into the local interconnect of the target LAB.
Logic Element
The logic element (LE) is the smallest unit of logic in the FLEX 8000
architecture, with a compact size that provides efficient logic utilization.
Each LE contains a 4-input LUT, a programmable flipflop, a carry chain,
and cascade chain. Figure 3 shows a block diagram of an LE.
Figure 3. FLEX 8000 LE
3
Carry-In Cascade-In
DATA1
DATA2
DATA3
DATA4
LABCTRL1
LABCTRL2
LABCTRL3
LABCTRL4
Look-Up
Table
(LUT)
Carry
Chain
Cascade
Chain
Clear/
Preset
Logic
Clock
Select
DFF
PRN
DQ
CLRN
LE-Out
Carry-Out Cascade-Out
The LUT is a function generator that can quickly compute any function of
four variables. The programmable flipflop in the LE can be configured for
D, T, JK, or SR operation. The clock, clear, and preset control signals on the
flipflop can be driven by dedicated input pins, general-purpose I/O pins,
or any internal logic. For purely combinatorial functions, the flipflop is
bypassed and the output of the LUT goes directly to the output of the LE.
Altera Corporation
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