Cyclone Device Handbook, Volume 1
The Quartus II Compiler automatically creates carry chain logic during
design processing, or you can create it manually during design entry.
Parameterized functions such as LPM functions automatically take
advantage of carry chains for the appropriate functions.
The Quartus II Compiler creates carry chains longer than 10 LEs by
linking LABs together automatically. For enhanced fitting, a long carry
chain runs vertically allowing fast horizontal connections to M4K
memory blocks. A carry chain can continue as far as a full column.
Clear & Preset Logic Control
LAB-wide signals control the logic for the register's clear and preset
signals. The LE directly supports an asynchronous clear and preset
function. The register preset is achieved through the asynchronous load
of a logic high. The direct asynchronous preset does not require a NOT-
gate push-back technique. Cyclone devices support simultaneous preset/
asynchronous load and clear signals. An asynchronous clear signal takes
precedence if both signals are asserted simultaneously. Each LAB
supports up to two clears and one preset signal.
In addition to the clear and preset ports, Cyclone devices provide a chip-
wide reset pin (DEV_CLRn) that resets all registers in the device. An
option set before compilation in the Quartus II software controls this pin.
This chip-wide reset overrides all other control signals.
In the Cyclone architecture, connections between LEs, M4K memory
blocks, and device I/O pins are provided by the MultiTrack interconnect
structure with DirectDriveTM technology. The MultiTrack interconnect
consists of continuous, performance-optimized routing lines of different
speeds used for inter- and intra-design block connectivity. The Quartus II
Compiler automatically places critical design paths on faster
interconnects to improve design performance.
MultiTrack
Interconnect
DirectDrive technology is a deterministic routing technology that ensures
identical routing resource usage for any function regardless of placement
within the device. The MultiTrack interconnect and DirectDrive
technology simplify the integration stage of block-based designing by
eliminating the re-optimization cycles that typically follow design
changes and additions.
The MultiTrack interconnect consists of row and column interconnects
that span fixed distances. A routing structure with fixed length resources
for all devices allows predictable and repeatable performance when
2–12
Preliminary
Altera Corporation
January 2007
ALTERA [ ALTERA CORPORATION ]
