ep1s25 Altera Corporation, ep1s25 Datasheet - Page 20

• Manufacturer Part Number: ep1s25
• Description: Stratix Device Family Data Sheet
• Manufacturer: Altera Corporation

Logic Elements
Figure 2–4. LAB-Wide Control Signals
Logic Elements
2–6
Stratix Device Handbook, Volume 1
Dedicated
Row LAB
Clocks
Local
Interconnect
Local
Interconnect
Local
Interconnect
Local
Interconnect
Local
Interconnect
Local
Interconnect
8
With the LAB-wide addnsub control signal, a single LE can implement a
one-bit adder and subtractor. This saves LE resources and improves
performance for logic functions such as DSP correlators and signed
multipliers that alternate between addition and subtraction depending
on data.
The LAB row clocks [7..0] and LAB local interconnect generate the LAB-
wide control signals. The MultiTrack
allows clock and control signal distribution in addition to data.
shows the LAB control signal generation circuit.
The smallest unit of logic in the Stratix architecture, the LE, is compact
and provides advanced features with efficient logic utilization. Each LE
contains a four-input LUT, which is a function generator that can
implement any function of four variables. In addition, each LE contains a
programmable register and carry chain with carry select capability. A
single LE also supports dynamic single bit addition or subtraction mode
selectable by an LAB-wide control signal. Each LE drives all types of
interconnects: local, row, column, LUT chain, register chain, and direct
link interconnects. See
labclk1
labclkena1
labclk2
Figure
labclkena2
2–5.
asyncload
or labpre
TM
syncload
interconnect’s inherent low skew
labclr1
labclr2
Altera Corporation
synclr
Figure 2–4
July 2005
addnsub