MAX 7000 Programmable Logic Device Family Data Sheet
The compiler can allocate up to three sets of up to five parallel expanders
automatically 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 8 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 8, the lowest-numbered macrocell can
only lend parallel expanders and the highest-numbered macrocell can
only borrow them. Figure 6 shows how parallel expanders can be
borrowed from a neighboring macrocell.
Figure 6. Parallel Expanders
Unused product terms in a macrocell can be allocated to a neighboring macrocell.
From
Previous
Macrocell
Preset
Product-
Term
Select
Matrix
Macrocell
Product-
Term Logic
Clock
Clear
Preset
Product-
Term
Select
Matrix
Macrocell
Product-
Term Logic
Clock
Clear
To Next
Macrocell
36 Signals 16 Shared
from PIA
Expanders
Altera Corporation
13
ALTERA [ ALTERA CORPORATION ]
