2–6
Chapter 2: MAX V Architecture
Logic Array Blocks
LAB Interconnects
Column and row interconnects and LE outputs within the same LAB drive the LAB
local interconnect. Adjacent LABs, from the left and right, can also drive an LAB’s
local interconnect through the DirectLink connection. The DirectLink connection
feature minimizes the use of row and column interconnects, providing higher
performance and flexibility. Each LE can drive 30 other LEs through fast local and
DirectLink interconnects. Figure 2–4 shows the DirectLink connection.
Figure 2–4. DirectLink Connection
DirectLink interconnect from
right LAB or IOE output
DirectLink interconnect from
left LAB or IOE output
LE0
LE1
LE2
LE3
LE4
LE5
LE6
LE7
LE8
LE9
DirectLink
interconnect
to left
DirectLink
interconnect
to right
Local
Interconnect
Logic Element
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, a
synchronous clear, an asynchronous preset/load, a synchronous load, and
add/subtract control signals, providing a maximum of 10 control signals at a time.
Synchronous load and clear signals are generally used when implementing counters
but they can also be used with other functions.
Each LAB can use two clocks and two clock enable signals. Each LAB’s clock and
clock enable signals are linked. For example, any LE in a particular LAB using the
labclk1signal also uses 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.
Each LAB can use two asynchronous clear signals and an asynchronous load/preset
signal. By default, the Quartus II software uses a NOTgate push-back technique to
achieve preset. If you disable the NOTgate push-back option or assign a given register
to power-up high using the Quartus II software, the preset is then achieved using the
asynchronous load signal with asynchronous load data input tied high.
MAX V Device Handbook
December 2010 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
