MAX 7000A Programmable Logic Device Data Sheet
Parallel Expanders
Parallel expanders are unused product terms that can be allocated to a
neighboring macrocell to implement fast, complex logic functions.
Parallel expanders allow up to 20 product terms to directly feed the
macrocell ORlogic, with five product terms provided by the macrocell and
15 parallel expanders provided by neighboring macrocells in the LAB.
The compiler can allocate up to three sets of up to five parallel expanders
to the macrocells that require additional product terms. Each set of five
parallel expanders incurs a small, incremental timing delay (tPEXP). For
example, if a macrocell requires 14 product terms, the compiler uses the
five dedicated product terms within the macrocell and allocates two sets
of parallel expanders; the first set includes five product terms, and the
second set includes four product terms, increasing the total delay by
2 × tPEXP
.
Two groups of eight macrocells within each LAB (e.g., macrocells 1
through 8 and 9 through 16) form two chains to lend or borrow parallel
expanders. A macrocell borrows parallel expanders from lower-
numbered macrocells. For example, macrocell 8 can borrow parallel
expanders from macrocell 7, from macrocells 7 and 6, or from macrocells
7, 6, and 5. Within each group of eight, the lowest-numbered macrocell
can only lend parallel expanders, and the highest-numbered macrocell
can only borrow them. Figure 4 shows how parallel expanders can be
borrowed from a neighboring macrocell.
Altera Corporation
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INTEL [ INTEL ]
