FLEX 10K Embedded Programmable Logic Device Family Data Sheet
Each LAB provides four control signals with programmable inversion
that can be used in all eight LEs. Two of these signals can be used as clocks;
the other two can be used for clear/preset control. The LAB clocks can be
driven by the dedicated clock input pins, global signals, I/O signals, or
internal signals via the LAB local interconnect. The LAB preset and clear
control signals can be driven by the global signals, I/O signals, or internal
signals via the LAB local interconnect. The global control signals are
typically used for global clock, clear, or preset signals because they
provide asynchronous control with very low skew across the device. 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. In
addition, the global control signals can be generated from LE outputs.
Logic Element
The LE, the smallest unit of logic in the FLEX 10K architecture, has a
compact size that provides efficient logic utilization. Each LE contains a
four-input LUT, which is a function generator that can quickly compute
any function of four variables. In addition, each LE contains a
programmable flipflop with a synchronous enable, a carry chain, and a
cascade chain. Each LE drives both the local and the FastTrack
Interconnect. See Figure 6.
Figure 6. FLEX 10K Logic Element
Register Bypass
Carry-In
Cascade-In
Programmable
Register
data1
data2
data3
data4
Look-Up
Table
(LUT)
To FastTrack
Interconnect
Carry
Chain
Cascade
Chain
PRN
D
Q
ENA
CLRN
To LAB Local
Interconnect
labctrl1
labctrl2
Clear/
Preset
Logic
Chip-Wide
Reset
Clock
Select
labctrl3
labctrl4
Carry-Out Cascade-Out
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