2–6
Chapter 2: Logic Elements and Logic Array Blocks in the Cyclone III Device Family
LAB Control Signals
Figure 2–5 shows the direct link connection.
Figure 2–5. Cyclone III Device Family Direct Link Connection
Direct link interconnect from
left LAB, M9K memory
block, embedded multiplier,
PLL, or IOE output
Direct link interconnect from
right LAB, M9K memory
block, embedded multiplier,
PLL, or IOE output
Direct link
interconnect
to left
Direct link
interconnect
to right
Local
Interconnect
LAB
LAB Control Signals
Each LAB contains dedicated logic for driving control signals to its LEs. The control
signals include:
■
■
■
■
■
Two clocks
Two clock enables
Two asynchronous clears
One synchronous clear
One synchronous load
You can use up to eight control signals at a time. Register packing and synchronous
load cannot be used simultaneously.
Each LAB can have up to four non-global control signals. You can use additional LAB
control signals as long as they are global signals.
Synchronous clear and load signals are useful for implementing counters and other
functions. The synchronous clear and synchronous load signals are LAB-wide signals
that affect all registers in the LAB.
Each LAB can use two clocks and two clock enable signals. The clock and clock enable
signals of each LAB are linked. For example, any LE in a particular LAB using the
labclk1signal also uses the labclkena1. If the LAB uses both the rising and falling
edges of a clock, it also uses both LAB-wide clock signals. Deasserting the clock
enable signal turns off the LAB-wide clock.
The LAB row clocks [5..0]and LAB local interconnect generate the LAB-wide
control signals. The MultiTrack interconnect inherent low skew allows clock and
control signal distribution in addition to data distribution.
Cyclone III Device Handbook
Volume 1
December 2011 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
