Chapter 2: Logic Elements and Logic Array Blocks in the Cyclone III Device Family
Logic Array Blocks
2–5
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LAB control signals
LE carry chains
Register chains
Local interconnect
The local interconnect transfers signals between LEs in the same LAB. Register chain
connections transfer the output of one LE register to the adjacent LE register in a LAB.
The Quartus II Compiler places associated logic in a LAB or adjacent LABs, allowing
the use of local and register chain connections for performance and area efficiency.
shows the LAB structure for the Cyclone III device family.
Figure 2–4. Cyclone III Device Family LAB Structure
Row Interconnect
Column
Interconnect
Direct link
interconnect
from adjacent
block
Direct link
interconnect
from adjacent
block
Direct link
interconnect
to adjacent
block
Direct link
interconnect
to adjacent
block
LAB
Local Interconnect
LAB Interconnects
The LAB local interconnect is driven by column and row interconnects and LE
outputs in the same LAB. Neighboring LABs, phase-locked loops (PLLs), M9K RAM
blocks, and embedded multipliers from the left and right can also drive the local
interconnect of a LAB through the direct link connection. The direct link connection
feature minimizes the use of row and column interconnects, providing higher
performance and flexibility. Each LE can drive up to 48 LEs through fast local and
direct link interconnects.
December 2011
Altera Corporation
Cyclone III Device Handbook
Volume 1
ALTERA [ ALTERA CORPORATION ]
