Lattice Semiconductor
Figure 6. Dual-OR PT Sharing Array
From Carry
n-7
In
From PT0
ispXPLD 5000MX Family Data Sheet
PT OE
To I/O Block
From PT1
PTSA Bypass
To Macrocell
From PT2
N
To PTSA
To Macrocell
PT Clock
From PT3
PT Preset
To Macrocell
From PT4
PT Reset
To Macrocell
To
n+7
Carry
Out
Product Term Sharing Array
The Product Term Sharing Array (PTSA) consists of 32 inputs from the Dual-OR Array (Expandable PTSA OR) and
32 outputs directly to the macrocells. Each output is the OR term of any combination of the seven Expandable
PTSA OR terms connected to that output. Every Nth macrocell is connected to N-3, N-2, N-1, N, N+1, N+2 and
N+3 PTSA OR terms via a programmable connection. This wraps around the logic, for example, Macrocell 0 gets
its logic from 29, 30, 31, 0, 1, 2, 3. The Expandable PTSA OR used in conjunction with the PTSA allows wide func-
tions to be implemented easily and ef铿乧iently. Without using the Expandable PTSA OR capability, the greatest
number of product terms that can be included in a single function with one pass of delay is 35. Up to 160 product
terms can be included in a single function through the use of the expandable PTSA OR capability. Figure 7 shows
the graphical representation of the PTSA.
Figure 7. Product Term Sharing Array (PTSA)
PTSA OR 0
PTSA OR 1
PTSA OR 2
PTSA OR 3
Macrocell 0
Macrocell 1
Macrocell 2
PTSA OR 29
PTSA OR 30
PTSA OR 31
Macrocell 29
Macrocell 30
Macrocell 31
7