M4A5-128/64-10YI LATTICE [Lattice Semiconductor], M4A5-128/64-10YI Datasheet - Page 7

• Manufacturer Part Number: M4A5-128/64-10YI
• Description: High Performance E 2 CMOS In-System Programmable Logic
• Manufacturer: LATTICE [Lattice Semiconductor]

Product-Term Array
The product-term array consists of a number of product terms that form the basis of the logic
being implemented. The inputs to the AND gates come from the central switch matrix (Table 5),
and are provided in both true and complement forms for efficient logic implementation.
Logic Allocator
Within the logic allocator, product terms are allocated to macrocells in “product term clusters.”
The availability and distribution of product term clusters are automatically considered by the
software as it fits functions within a PAL block. The size of a product term cluster has been
optimized to provide high utilization of product terms, making complex functions using many
product terms possible. Yet when few product terms are used, there will be a minimal number
of unused—or wasted—product terms left over. The product term clusters available to each
macrocell within a PAL block are shown in Tables 6 and 7.
Each product term cluster is associated with a macrocell. The size of a cluster depends on the
configuration of the associated macrocell. When the macrocell is used in synchronous mode
(Figure 2a), the basic cluster has 4 product terms. When the associated macrocell is used in
asynchronous mode (Figure 2b), the cluster has 2 product terms. Note that if the product term
cluster is routed to a different macrocell, the allocator configuration is not determined by the
mode of the macrocell actually being driven. The configuration is always set by the mode of the
macrocell that the cluster will drive if not routed away, regardless of the actual routing.
In addition, there is an extra product term that can either join the basic cluster to give an
extended cluster, or drive the second input of an exclusive-OR gate in the signal path. If included
with the basic cluster, this provides for up to 20 product terms on a synchronous function that
uses four extended 5-product-term clusters. A similar asynchronous function can have up to 18
product terms.
When the extra product term is used to extend the cluster, the value of the second XOR input
can be programmed as a 0 or a 1, giving polarity control. The possible configurations of the logic
allocator are shown in Figures 3 and 4.
M4A3-32/32 and M4A5-32/32
M4A3-64/32 and M4A5-64/32
M4A3-64/64
M4A3-96/48 and M4A5-96/48
M4A3-128/64 and M4A5-128/64
M4A3-192/96 and M4A5-192/96
M4A3-256/128 and M4A5-256/128
M4A3-256/160 and M4A3-256/192
M4A3-384
M4A3-512
Device
Table 5. PAL Block Inputs
ispMACH 4A Family
Number of Inputs to PAL Block
33
33
33
33
33
34
34
36
36
36
7