Lattice Semiconductor
Product Term Allocator
ispMACH 4000V/B/C/Z Family Data Sheet
The product term allocator assigns product terms from a cluster to either logic or control applications as required
by the design being implemented. Product terms that are used as logic are steered into a 5-input OR gate associ-
ated with the cluster. Product terms that used for control are steered either to the macrocell or I/O cell associated
with the cluster. Table 3 shows the available functions for each of the five product terms in the cluster. The OR gate
output connects to the associated I/O cell, providing a fast path for narrow combinatorial functions, and to the logic
allocator.
Table 3. Individual PT Steering
Product Term
PT
n
PT
n
+1
PT
n
+2
PT
n
+3
PT
n
+4
Logic
Logic PT
Logic PT
Logic PT
Logic PT
Logic PT
Single PT for XOR/OR
Individual Clock (PT Clock)
Individual Initialization or Individual Clock Enable (PT Initialization/CE)
Individual Initialization (PT Initialization)
Individual OE (PTOE)
Control
Cluster Allocator
The cluster allocator allows clusters to be steered to neighboring macrocells, thus allowing the creation of functions
with more product terms. Table 4 shows which clusters can be steered to which macrocells. Used in this manner,
the cluster allocator can be used to form functions of up to 20 product terms. Additionally, the cluster allocator
accepts inputs from the wide steering logic. Using these inputs, functions up to 80 product terms can be created.
Table 4. Available Clusters for Each Macrocell
Macrocell
M0
M1
M2
M3
M4
M5
M6
M7
M8
M9
M10
M11
M12
M13
M14
M15
—
C0
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C0
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
Available Clusters
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
—
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
C14
C15
—
—
Wide Steering Logic
The wide steering logic allows the output of the cluster allocator n to be connected to the input of the cluster alloca-
tor
n
+4. Thus, cluster chains can be formed with up to 80 product terms, supporting wide product term functions
and allowing performance to be increased through a single GLB implementation. Table 5 shows the product term
chains.
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LATTICE [ LATTICE SEMICONDUCTOR ]
